Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Mar. 07, 2018	Jun. 30, 2017
Document And Entity Information
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	mram
Entity Registrant Name	EVERSPIN TECHNOLOGIES INC
Entity Central Index Key	0001438423
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 179.5
Entity Common Stock, Shares Outstanding		16,635,651

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 12,950	$ 29,727
Accounts receivable, net	3,429	3,170
Amounts due from related parties	612	486
Inventory	9,837	5,069
Prepaid expenses and other current assets	590	1,050
Total current assets	27,418	39,502
Property and equipment, net	3,946	1,920
Other assets	73	50
Total assets	31,437	41,472
Current liabilities:
Accounts payable	2,720	1,502
Accrued liabilities	2,254	1,811
Amounts due to related parties	1,694	1,359
Deferred income on shipments to distributors	1,720	1,827
Current portion of long-term debt	3,987	3,884
Total current liabilities	12,375	10,383
Long-term debt, net of current portion	8,178	4,218
Total liabilities	20,553	14,601
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized as of December 31, 2017 and 2016; no shares issued and outstanding as of December 31, 2017 and 2016
Common stock, $0.0001 par value per share; 100,000,000 shares authorized as of December 31, 2017 and 2016; 12,817,201 and 12,498,128 shares issued and outstanding as of December 31, 2017 and 2016	1	1
Additional paid-in capital	128,422	123,309
Accumulated deficit	(117,539)	(96,439)
Total stockholders' equity	10,884	26,871
Total liabilities and stockholders' equity	$ 31,437	$ 41,472

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Balance Sheets
Preferred Stock, Par Value	$ 0.0001	$ 0.0001
Preferred Stock, Shares Authorized	5,000,000	5,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	12,817,201	12,498,128
Common stock, shares outstanding	12,817,201	12,498,128

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Product sales	$ 31,361	$ 24,233	$ 22,403
Licensing and royalty revenue	634	483	671
Total revenue	35,936	27,094	26,546
Cost of sales	14,451	12,395	12,568
Gross profit	21,485	14,699	13,978
Operating expenses:
Research and development	25,437	19,233	21,126
General and administrative	11,516	7,281	6,565
Sales and marketing	4,740	3,706	3,823
Total operating expenses	41,693	30,220	31,514
Loss from operations	(20,208)	(15,521)	(17,536)
Interest expense	(764)	(2,347)	(653)
Other income, net	118	1,160	6
Loss on extinguishment of debt	(246)
Net loss and comprehensive loss	$ (21,100)	$ (16,708)	$ (18,183)
Net loss per common share, basic and diluted	$ (1.69)	$ (3.53)	$ (7.12)
Weighted-average shares used to compute net loss per common share, basic and diluted	12,484,984	4,738,496	2,552,205
Related Party
Product sales	$ 2,316	$ 2,378	$ 3,472
Licensing and royalty revenue	$ 1,625

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Global Foundries Additional Paid-In Capital	Global Foundries	Common Stock Initial Public Offering	Common Stock Private Placement	Common Stock	Additional Paid-In Capital Initial Public Offering	Additional Paid-In Capital Private Placement	Additional Paid-In Capital	Accumulated Deficit	Initial Public Offering	Private Placement	Total
Balance at Dec. 31, 2014								$ 7,120,000	$ (61,548,000)			$ (54,428,000)
Balance (in shares) at Dec. 31, 2014					3,013,723
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)					1,558
Issuance of common stock upon exercise of stock options								4,000				4,000
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES								1,761,000				1,761,000
Stock-based compensation expense								416,000				416,000
Net loss					$ 0			0	(18,183,000)			(18,183,000)
Balance at Dec. 31, 2015								9,301,000	(79,731,000)			(70,430,000)
Balance (in shares) at Dec. 31, 2015					3,015,281
Increase (Decrease) in Stockholders' Equity
Conversion of redeemable convertible preferred stock to common stock								64,642,000				64,642,000
Conversion of redeemable convertible preferred stock to common stock (in shares)					2,486,199
Conversion of convertible promissory notes to common stock								8,634,000				8,634,000
Conversion of convertible promissory notes to common stock (in shares)					1,361,009
Reclassification of redeemable convertible preferred stock warrant liability to additional paid in capital								65,000				65,000
Issuance of common stock			$ 1,000			$ 33,863,000	$ 4,650,000			$ 33,864,000	$ 4,650,000
Issuance of common stock (in shares)			5,000,000	625,000	10,639
Issuance of common stock upon exercise of stock options								48,000				$ 48,000
Issuance of common stock upon exercise of stock options (in shares)												10,639
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES	$ 965,000	$ 965,000
Stock-based compensation expense								1,141,000				$ 1,141,000
Net loss									(16,708,000)			(16,708,000)
Balance at Dec. 31, 2016					$ 1,000			123,309,000	(96,439,000)			26,871,000
Balance (in shares) at Dec. 31, 2016					12,498,128
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options								1,337,000				$ 1,337,000
Issuance of common stock upon exercise of stock options (in shares)					281,483							281,483
Issuance of common stock under Employee Stock Purchase Plan								256,000				$ 256,000
Issuance of common stock under Employee Stock Purchase Plan (in shares)					37,590
Compensation expense related to vesting of common stock issued to GLOBALFOUNDRIES								1,472,000				1,472,000
Stock-based compensation expense								2,048,000				2,048,000
Net loss									(21,100,000)			(21,100,000)
Balance at Dec. 31, 2017					$ 1,000			$ 128,422,000	$ (117,539,000)			$ 10,884,000
Balance (in shares) at Dec. 31, 2017					12,817,201

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - Redeemable - USD ($) $ in Thousands	Redeemable Convertible Preferred Stock	Total
Balance at Dec. 31, 2014	$ 64,642
Balance (in shares) at Dec. 31, 2014	2,486,199
Increase (Decrease) in Redeemable Convertible Preferred Stock
Net loss	$ 0	$ (18,183)
Balance at Dec. 31, 2015	$ 64,642
Balance (in shares) at Dec. 31, 2015	2,486,199
Increase (Decrease) in Redeemable Convertible Preferred Stock
Conversion of redeemable convertible preferred stock to common stock	$ (64,642)	64,642
Conversion of redeemable convertible preferred stock to common stock (in shares)	(2,486,199)
Net loss		$ (16,708)
Balance at Dec. 31, 2016	$ 0
Balance (in shares) at Dec. 31, 2016	0

Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statement of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net loss	$ (21,100)	$ (16,708)	$ (18,183)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,191	826	1,340
Loss on disposal of property and equipment		80
Stock-based compensation	2,048	1,141	416
Change in fair value of redeemable convertible preferred stock warrant liability		(372)	(15)
Non-cash loss on extinguishment of debt	185
Change in fair value of derivative liability		(798)
Non-cash interest expense	297	1,183	232
Compensation expense related to vesting of common stock to GLOBALFOUNDRIES	1,472	965	1,761
Changes in operating assets and liabilities:
Accounts receivable	(259)	(1,261)	339
Amounts due from related parties	(126)	78	102
Inventory	(3,871)	(893)	(431)
Prepaid expenses and other current assets	460	(860)	(77)
Other assets	(23)	(21)	(10)
Accounts payable	1,114	340	233
Accrued liabilities	(120)	56	428
Amounts due to related parties	(49)	(2,453)	3,328
Deferred income on shipments to distributors	(107)	387	(362)
Deferred revenue		(229)	229
Net cash used in operating activities	(18,888)	(18,539)	(10,670)
Cash flows from investing activities
Purchases of property and equipment	(3,070)	(1,040)	(1,295)
Net cash used in investing activities	(3,070)	(1,040)	(1,295)
Cash flows from financing activities
Proceeds from convertible promissory notes-related party		8,500
Proceeds from debt	12,000	1,500	8,000
Payments on debt	(8,356)	(1,325)	(3,000)
Payments of debt issuance costs	(49)	(40)	(130)
Payments on capital lease obligation	(7)	(198)	(226)
Proceeds from exercise of stock options and purchase of shares in employee stock purchase plan	1,593	48	4
Proceeds from issuance of common stock in connection with initial public offering, net of offering costs		33,864
Proceeds from issuance of common stock in private placement, net of issuance costs		4,650
Net cash provided by financing activities	5,181	46,999	4,648
Net (decrease) increase in cash and cash equivalents	(16,777)	27,420	(7,317)
Cash and cash equivalents at beginning of period	29,727	2,307	9,624
Cash and cash equivalents at end of period	12,950	29,727	2,307
Supplementary cash flow information:
Interest paid	467	806	421
Interest paid to related party		359
Non-cash investing and financing activities:
Purchase of property and equipment in accounts payable and amounts due to related parties	116
Purchase of inventory in accrued liabilities and amounts due to related parties	897
Purchase of property and equipment under capital lease obligations	$ 31		431
Conversion of convertible promissory notes into common stock		8,634
Issuance of warrants with debt			$ 307
Conversion of redeemable convertible preferred stock into common stock		64,642
Reclassification of warrant liability to additional paid-in capital		$ 65

Organization and Operations

12 Months Ended

Dec. 31, 2017

Organization and Operations

Organization and Operations

1. Organization and Operations

Everspin Technologies, Inc. (the Company) was incorporated in Delaware on May 16, 2008. The Company’s magnetoresistive random access memory (MRAM) solutions offer the persistence of non-volatile memory with the speed and endurance of random access memory (RAM) and enable the protection of mission critical data particularly in the event of power interruption or failure. The Company’s MRAM products allow its customers in the industrial, automotive and transportation, and enterprise storage markets to design high performance, power efficient and reliable systems without the need for bulky batteries or capacitors.

Reverse Stock Split

In September 2016, the Company effected a 1-for-26 reverse stock split of all outstanding shares of the Company’s capital stock, including common stock and redeemable convertible preferred stock. All share, option, convertible promissory notes, warrant, and per share information presented in the financial statements has been adjusted to reflect the stock split on a retroactive basis for all periods presented and all share information is rounded down to the nearest whole share after reflecting the stock split.

Initial Public Offering and Concurrent Private Placement

On October 7, 2016, the Company’s Registration Statement on Form S‑1 (File No. 333‑213569) relating to the initial public offering, (IPO), of its common stock was declared effective by the Securities and Exchange Commission (SEC). Pursuant to such Registration Statement, the Company sold 5,000,000 shares at an initial public offering price of $8.00 per share for net proceeds of $33.9 million to the Company, net of underwriting discounts and commissions, and offering costs. Concurrent with the IPO, the Company issued 625,000 shares of its common stock in a private placement for net proceeds of $4.7 million, after deducting the placement agent fee.

In connection with the IPO, the following events occurred:

An aggregate of 2,486,199 shares of the Company’s common stock were issued to the holders of the redeemable convertible preferred stock upon the conversion of all shares of redeemable convertible preferred stock into common stock immediately prior to the closing of the IPO.

The outstanding balance of the convertible promissory notes payable including accrued interest was converted into 1,361,009 shares of common stock.

All of the outstanding redeemable convertible preferred stock warrants converted to warrants to purchase shares of common stock upon the closing of the IPO.

Ability to continue as a going concern

The Company believes that its existing cash and cash equivalents as of December 31, 2017, coupled with its anticipated growth and sales levels, and proceeds of $24.8 million to the Company, net of underwriting discounts and commissions, but before offering costs from the follow-on underwritten public offering in February 2018, will be sufficient to meet its anticipated cash requirements for at least the next 12 months from March 15, 2018. The Company’s future capital requirements will depend on many factors, including its growth rate, the timing and extent of its spending to support research and development activities, the timing and cost of establishing additional sales and marketing capabilities, and the introduction of new products. The Company may be required at some point in the future to seek additional equity or debt financing, to sustain operations beyond that point, and such additional financing may not be available on acceptable terms or at all. If the Company is unable to raise additional capital or generate sufficient cash from operations to adequately fund its operations, it will need to curtail planned activities to reduce costs. Doing so will likely harm its ability to execute on its business plan.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP). The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, fair value of assets and liabilities, inventory, product warranty reserves, income taxes, and stock-based compensation. Actual results could differ from those estimates and assumptions.

Segments

The Company’s chief operating decision maker is its Chief Executive Officer. The Company operates its business as one operating segment for purposes of assessing performance and making operating decisions. All of the Company’s assets are maintained in the United States. The Company derives its revenue from domestic and international markets, based on the billing address of the customer.

Cash and Cash Equivalents

The Company considers all highly liquid, short-term investments with maturity dates of three months or less at the date of purchase to be cash equivalents. The Company’s cash equivalents consist of money market funds.

Accounts Receivable

Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company generally does not require collateral or other security in support of accounts receivable. Allowances are provided for individual accounts receivable when the Company becomes aware of a customer’s inability to meet its financial obligations, such as in the case of bankruptcy, deterioration in the customer’s operating results or change in financial position. If circumstances related to customers change, estimates of the recoverability of receivables would be further adjusted. The Company also considers a number of factors in evaluating the sufficiency of its allowance for doubtful accounts, including the length of time receivables are past due, significant one-time events, creditworthiness of customers and historical experience. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. At December 31, 2017 and 2016, there was no allowance for doubtful accounts.

The Company also establishes an allowance for product returns. The Company analyzes historical returns, current economic trends and changes in customer demand and acceptance of products when evaluating the adequacy of sales returns. As the returns are processed as credits on future purchases, the allowance is recorded against the balance of trade accounts receivable. The allowance was $147,000 and $188,000 at December 31, 2017 and 2016, respectively.

Concentration of Credit Risk

Financial instruments that potentially expose the Company to a concentration of credit risk consist principally of cash and cash equivalents that are held by a financial institution in the United States and accounts receivable. Amounts on deposit with a financial institution may at times exceed federally insured limits. The Company maintains its cash accounts with high credit quality financial institutions and accordingly, minimal credit risk exists with respect to the financial institutions.

Significant customers are those which represent more than 10% of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the purposes of this disclosure, the Company defines “customer” as the entity that is purchasing the products directly from the Company, which includes the distributors of the Company’s products in addition to end customers that the Company sells to directly. For each significant customer, revenue as a percentage of total revenue and accounts receivable as a percentage of total accounts receivable, net are as follows:


	Revenue						Accounts Receivable
	Year Ended December 31,						December 31,
Customers	2017		2016		2015		2017		2016
Customer A	15	%	22	%	26	%	*	%	12	%
Customer B	*		*		13		15		13
Customer C	*		*		*		10		10
Customer D	16		12		*		*		18

*Less than 10%

Inventory

Inventory is valued at the lower of cost, using the first-in, first-out or specific identification method, or market. The carrying value of inventory is adjusted for excess and obsolete inventory based on inventory age, shipment history and the forecast of demand over a specific future period. At the point of loss recognition, a new lower cost basis for that inventory is established and subsequent changes in facts and circumstances do not result in the restoration or increase in that new cost basis.

Fair Value of Financial Instruments

The Company discloses and recognizes the fair value of its assets and liabilities using a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The hierarchy gives the highest priority to valuations based upon unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to valuations based upon unobservable inputs that are significant to the valuation (Level 3 measurements). The guidance establishes three levels of the fair value hierarchy as follows:

Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Inputs (other than quoted market prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life.

Level 3—Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

The carrying value of accounts receivable, accounts payable, and other accruals readily convertible into cash approximate fair value because of the short-term nature of the instruments. The carrying value of the Company’s variable interest rate debt, excluding unamortized debt issuance costs, approximates fair value. The Company’s financial instruments consist of Level 1 assets. Where quoted prices are available in an active market, securities are classified as Level 1. Level 1 assets consist primarily of highly liquid money market funds that are included in cash equivalents.

The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands):


	December 31, 2017
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	13,369	$	—	$	—	$	13,369
Total assets measured at fair value	$	13,369	$	—	$	—	$	13,369


	December 31, 2016
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	29,869	$	—	$	—	$	29,869
Total assets measured at fair value	$	29,869	$	—	$	—	$	29,869

The following table sets forth a summary of the changes in the fair value of the redeemable convertible preferred stock warrant liability, a Level 3 financial liability, which is measured on a recurring basis (in thousands):


	December 31,
	2017		2016		2015
Beginning balance	$	—	$	437	$	145
Issuance of redeemable convertible preferred stock warrants		—		—		307
Change in fair value recorded in other income, net		—		(372)		(15)
Reclassification to additional paid-in capital		—		(65)		—
Ending balance	$	—	$	—	$	437

The key assumptions used in the Black-Scholes option-pricing model for the valuation of the redeemable convertible preferred stock warrants were:


	Year Ended December 31,
	2017			2016			2015
Expected volatility		—	%		42.4 – 52.0	%		43.6 – 52.9	%
Risk-free interest rate		—	%		1.22 – 1.86	%		1.76 – 2.27	%
Expected term (in years)		—			4 – 9			5 – 10
Exercise price	$	—		$	26.00		$	26.00
Dividend yield		—	%		—	%		—	%

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation begins at the time the asset is placed in service. Maintenance and repairs are charged to operations as incurred. Depreciation is computed using the straight-line method over the following estimated useful lives of the assets:


	Useful Lives
Computer and network equipment		2 years
Manufacturing equipment		2 – 7 years
Furniture and fixtures		7 years
Software		3 years

Leasehold improvements are amortized over the shorter of the lease term or useful life. Upon sale or retirement of assets, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is reflected in operations. Amortization expense of assets acquired through capital leases is included in the statements of operations and comprehensive loss.

Impairment of Long-lived Assets

The Company evaluates its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows the asset is expected to generate over its remaining life. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. There have been no impairments of the Company’s long-lived assets during any of the periods presented.

Intangible Assets

Intangible assets consist of the cost of acquired technology for use in research and development activities. Costs associated with patent applications, patent prosecution, patent defense and maintenance of patents are charged to expense as incurred. Intangible assets were fully amortized as of December 31, 2016.

Redeemable Convertible Preferred Stock Warrant Liability

Warrants for shares that were contingently redeemable were classified as liabilities on the balance sheet at their estimated fair value because the shares underlying the warrants may have obligated the Company to transfer assets to the holders at a future date under certain circumstances such as a deemed liquidation event. The warrants were subject to re-measurement at each balance sheet date and the change in fair value, if any, was recognized as other income, net in the statements of operations. The Company adjusted the liability for changes in fair value until the completion of the IPO in October 2016, at which time all redeemable convertible preferred stock warrants were converted into warrants to purchase common stock and the liability was reclassified to additional paid-in capital and no longer subject to remeasurement.

Revenue Recognition

The Company recognizes revenue when the following criteria are met: persuasive evidence of an arrangement exists; the price is fixed or determinable; delivery has occurred and title passed; and collectibility is reasonably assured. For sales to original equipment manufacturers (OEMs) and contract manufacturers, this occurs generally upon shipment. Provisions for product returns and allowances are recorded in the same period as related revenues. The Company analyzes historical returns, current economic trends and changes in customer demand and acceptance of product when evaluating the adequacy of sales returns and other allowances, which are netted against accounts receivable, as these are processed as credits against future purchases or balances outstanding.

The Company sells the majority of its products to its distributors at a uniform list price. However, distributors resell the Company’s products to end customers at a very broad range of individually negotiated price points. Distributors are provided with price concessions subsequent to delivery of product to them depending on their end customer and sales price. These concessions are based on a variety of factors, including customer, product, quantity, geography and competitive differentiation. Price protection rights grant distributors the right to a credit in the event of declines in the price of the Company’s products. Under these circumstances, the Company remits back to the distributor a portion of their original purchase price after the resale transaction is completed in the form of a credit against the distributors’ outstanding accounts receivable balance. The credits are on a per unit basis and are not given to the distributor until the distributor provides information regarding the sale to their end customer. Revenue on shipments to distributors is deferred as the price is not fixed or determinable until delivery has been made by the distributor to its customer and the final sales price has been established.

At the time of shipment to distributors, the Company records a trade receivable for the selling price as there is a legally enforceable obligation of the distributor to pay for the product delivered, inventory is reduced by the carrying value of goods shipped, and the net of these amounts, the gross profit, is recorded as deferred income on shipments to distributors on the balance sheet. The amount of gross profit that will be ultimately recognized in the statements of operations on such sales could be lower than the deferred income recorded on the balance sheets as a result of credits granted to distributors from the price protection rights. The Company is unable to estimate the credits to the distributors due to the wide variability of negotiated price concessions granted to them.

Thus, a portion of the “deferred income on shipments to distributors” balance represents the amount of distributors’ original purchase price that will be credited back to the distributor in the future. The wide range and variability of negotiated price concessions granted to distributors does not allow the Company to accurately estimate the portion of the balance in the deferred income on shipments to distributor accounts that will be credited back to the distributor. Therefore, the Company does not reduce deferred income on shipments to distributors or accounts receivable by anticipated future price concessions rather, price concessions are recorded against deferred income on shipments to distributors when incurred, which is generally at the time the distributor sells the product.

At December 31, 2017, the Company had $2.6 million of deferred revenue and $0.9 million of deferred cost of sales recognized as $1.7 million of deferred income on shipments to distributors. At December 31, 2016, the Company had $2.9 million of deferred revenue and $1.1 million of deferred cost of sales recognized as $1.8 million of deferred income on shipments to distributors.

Products returned by distributors and subsequently scrapped have historically been immaterial to the Company’s results of operations. The Company routinely evaluates the risk of impairment of the deferred cost of sales component of the deferred income on shipments to distributors account. Because of the historically immaterial amounts of inventory that have been scrapped, and historically rare instances where discounts given to a distributor result in a price less than our cost, the Company believes the deferred costs are recorded at their approximate carrying values.

For licenses of technology, recognition of revenue is dependent upon whether the Company delivered rights to the technology, and whether there are future performance obligations. In some instances, the license agreements call for future milestones to be met for amounts to be due from the customer. In such scenarios, revenue is recognized using the milestone method, whereby revenue is recognized upon the completion of substantive milestones once the customers acknowledge the milestones have been met and the collection of the amounts are reasonably assured. Royalties received are recognized when reported to the Company, which generally coincides with the receipt of payment.

Product Warranty

The Company generally sells products with a limited warranty of product quality and a limited indemnification of customers against intellectual property infringement claims related to the Company’s products. The Company accrues for known warranty and indemnification issues if a loss is probable and can be reasonably estimated, and accrues for estimated losses incurred for unidentified issues based on historical experience. A warranty liability was not recorded at December 31, 2017 and 2016, as the estimated future warranty costs were insignificant based on the Company’s historical experience.

Research and Development

Research and development expenses are incurred in support of internal development programs or as part of our joint development agreement with GLOBALFOUNDRIES (see Note 9). Research and development expenses include personnel-related costs (including stock-based compensation), circuit design costs, purchases of materials and laboratory supplies, fabrication and packaging of experimental integrated circuit products, depreciation of research and development related capital equipment and overhead, and are expensed as incurred.

Stock-based Compensation

Stock-based compensation arrangements include stock option grants and restricted stock unit (RSU) awards under our equity incentive plans, as well as shares issued under our Employee Stock Purchase Plan (ESPP), through which employees may purchase our common stock at a discount to the market price.

The Company measures its stock-based awards made to employees based on the estimated fair value of the awards as of the grant date using the Black-Scholes option-pricing model. Stock-based compensation expense is recognized over the requisite service period using the straight-line method. The Company has made an accounting policy election to account for forfeitures as they occur, rather than estimating expected forfeitures at the time of the grant.

Stock-based compensation expense for options granted to non-employees as consideration for services received is measured on the date of performance at the fair value of the consideration received or the fair value of the equity instruments issued, using the Black-Scholes option-pricing model, whichever can be more reliably measured. Compensation expense for options granted to non-employees is periodically remeasured as the underlying options vest.

Income Taxes

The Company uses the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company must then assess the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s lack of earnings history, the net deferred tax assets have been fully offset by a valuation allowance.

The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merits, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

The SEC staff issued Staff Accounting Bulletin No. 118 (SAB 118) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act (2017 Tax Act). SAB 118 provides a measurement period that should not extend beyond one year from the 2017 Tax Act enactment date for companies to complete the accounting for the income tax effects of certain elements of the 2017 Tax Act. In accordance with SAB 118, the Company has recognized the provisional tax impacts related to the remeasurement of deferred tax assets and liabilities and included these amounts in its financial statements for the year ended December 31, 2017. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the 2017 Tax Act. See Note 11 for additional discussion on the provisional effects of the 2017 Tax Act.

Comprehensive Loss

Comprehensive loss represents all changes in stockholders’ equity (deficit) except those resulting from and distributions to stockholders. The Company’s comprehensive loss was equal to its net loss for all periods presented.

Net Loss per Common Share

Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period less shares subject to repurchase, without consideration of potentially dilutive securities. Diluted net loss per common share is the same as basic net loss per common share since the effect of potentially dilutive securities is anti-dilutive.

Recently Issued Pronouncements

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014‑09, Revenue from Contracts with Customers. Areas of revenue recognition that will be affected include, but are not limited to, transfer of control, variable consideration, allocation of transfer pricing, licenses, time value of money, contract costs and disclosures. The new standard permits adoption either by using (i) a full retrospective approach for all periods presented in the period of adoption or (ii) a modified retrospective approach with the cumulative effect of initially applying the new standard recognized at the date of initial application and providing certain additional disclosures. The new standard is effective for annual reporting periods beginning after December 15, 2017, with early adoption permitted for annual reporting periods beginning after December 15, 2016. As described in the Company's significant accounting policies, the Company currently defers the revenue and cost of sales on shipments to distributors until the distributor sells the product to their end customer.

The Company plans to adopt ASU 2014-09 and its amendments on January 1, 2018 under the modified retrospective approach, applying the amendments to prospective reporting periods.

Upon adoption, the Company expects a material impact to the opening balance sheet as of January 1, 2018, related to the cumulative effect of adopting the standard, primarily as a result of the items discussed below. The Company will continue to assess and complete the review of all potential impacts of the standard including the tax related impact. The most significantly impacted areas are the following:

Distributor sales: Under ASU 2014-09, the Company will recognize revenue from sales to distributors upon delivery of the product to the distributor, rather than upon delivery of the product to the end customer. At December 31, 2017, the deferred income on shipments to distributors under Topic 605 related to shipments to distributors that had not sold through to end-users is $1.7 million. Concessions and price protection credits offered to distributors, which are earned when sales to end customers are completed, will be estimated at the point of revenue recognition and impact is estimated to be $200,000 to $400,000 as of December 31, 2017 and will be a direct offset to the deferred income mentioned above. Since the Company will recognize revenue when control of the products transfer to the distributor under ASU 2014-09, the majority of this amount will be eliminated as a cumulative effect adjustment of implementing ASU 2014-09 as of January 1, 2018, net of the Company’s estimate of such concessions and price protection.

Product delivered over time: Under ASU 2014-09, Topic 605 permitted straight-line recognition of revenue for performance obligations that are delivered over time. The new standard requires an entity to recognize revenue based on the pattern of transfer of the services. The Company is expecting a minimal impact upon adoption.

The Company does not expect the changes described above to have a material impact on its quarterly and/or annual statement of operations, however the exact impact of ASU 2014-09 will be dependent on facts and circumstances that could vary from quarter to quarter.

In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718) Scope of Modification Accounting, which is intended to amend the scope of modification accounting for share-based payment arrangements. The amendments in the update provide guidance on types of changes to the terms or conditions of share-based payment awards that would require the Company to apply modification accounting under ASC 718, Compensation-Stock Compensation. This ASU is effective for annual reporting periods beginning after December 15, 2017, and early adoption is permitted. The Company plans on adopting this standard on January 1, 2018, and the impact of its adoption on the Company’s financial statements is not expected to be material.

In February 2016, the FASB issued ASU No. 2016‑02, Leases, which establishes a comprehensive new lease accounting model. The new standard: (a) clarifies the definition of a lease; (b) requires a dual approach to lease classification similar to current lease classifications; and (c) causes lessees to recognize leases on the balance sheet as a lease liability with a corresponding right-of-use asset for leases with a lease-term of more than twelve months. This ASU is effective for fiscal years and interim periods within those years beginning after December 15, 2018. The Company is currently evaluating the impact that the adoption of ASU 2016‑02 will have on its financial statements and related disclosures.

In June 2016, the FASB issued ASU No. 2016‑13, Financial Instruments – Credit Losses (Topic 326), which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. The new standard replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. The amended guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016‑13 will have on its financial statements and related disclosures.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. ASU 2016-15 identifies how certain cash receipts and cash payments are presented and classified in the Statement of Cash Flows. The standard is effective for fiscal years and interim periods beginning after December 15, 2017. The standard should be applied retrospectively and early adoption is permitted, including adoption in an interim period. The Company plans on adopting this standard on January 1, 2018, and the impact of its adoption on the Company’s financial statements is not expected to be material.

Recently Adopted Pronouncements

In July 2015, the FASB issued ASU No. 2015‑11, Simplifying the Measurement of Inventory, which requires an entity to measure in scope inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. This ASU is effective for fiscal years and interim periods within those years beginning after December 15, 2016. The Company adopted this standard as of January 1, 2017, and the impact of its adoption on the Company’s financial statements was not material.

In November 2015, FASB issued ASU No. 2015‑17, Balance Sheet Classification of Deferred Taxes, which is intended to simplify and improve how deferred taxes are classified on the balance sheet. The guidance in this ASU eliminates the current requirement to present deferred tax assets and liabilities as current and noncurrent in a classified balance sheet and now requires entities to classify all deferred tax assets and liabilities as noncurrent. The guidance is effective for annual periods beginning after December 15, 2016, and for interim periods within those annual periods. Early adoption is permitted. The Company adopted this standard as of January 1, 2017, and the impact of its adoption on the Company’s financial statements was not material.

In March 2016, the FASB issued ASU No. 2016‑09, Compensation-Stock Compensation (Topic 718) Improvements to Employee Share-Based Payment Accounting, which is intended to simplify several aspects of the accounting for employee share-based payment transactions, including the income tax consequences, the determination of forfeiture rates, classification of awards as either equity or liabilities, and classification on the statement of cash flows. This ASU is effective for fiscal years and interim periods within those years beginning after December 15, 2016, and early adoption is permitted. The Company adopted this standard as of January 1, 2017, and the impact of its adoption on the Company’s financial statements was not material.

Balance Sheet Components

12 Months Ended

Dec. 31, 2017

Balance Sheet Components

Balance Sheet Components

3. Balance Sheet Components

Inventory

Inventory consisted of the following (in thousands):


	December 31,
	2017		2016
Raw materials	$	682	$	853
Work-in-process		4,517		3,152
Finished goods		4,638		1,064
Total inventory	$	9,837	$	5,069

Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2017		2016
Manufacturing equipment	$	10,465	$	8,983
Computer and network equipment		710		588
Furniture and fixtures		218		188
Software		455		333
Leasehold improvements		1,474		13
Total property and equipment, gross		13,322		10,105
Less: accumulated depreciation		(9,376)		(8,185)
Total property and equipment, net	$	3,946	$	1,920

Depreciation and amortization expense during the years ended December 31, 2017, 2016 and 2015 was $1.2 million, $0.7 million and $1.2 million, respectively.

Intangible Assets, Net

In 2008, the Company spun-out of Freescale Semiconductor, Inc. (Freescale, a wholly-owned subsidiary of NXP Semiconductors N.V.) and acquired certain intellectual property assets and related licenses used in the MRAM business of Freescale. The value assigned to these acquired intangible assets was $910,000. Intangible assets were fully amortized as of December 31, 2016.

Amortization expense was $0, $132,000 and $150,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2017		2016
Accrued payroll-related expenses	$	1,331	$	1,045
Deferred licensing revenue		—		229
Deferred rent		230		248
Accrued sales commissions payable to sales representatives		75		193
Other		618		96
Total accrued liabilities	$	2,254	$	1,811

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies

Commitments and Contingencies

4. Commitments and Contingencies

Operating Leases

The Company leases office space for its corporate headquarters located in Chandler, Arizona and for its design facility located in Austin, Texas. The leases expire January 2022. Rent expense is recognized on a straight-line basis over the term of the leases and accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability.

In January 2017, the Company entered into a five-year sublease agreement with Freescale, a related party, to rent 6,560 square feet of office and laboratory space in Chandler, Arizona, and in March 2017, the Company amended the sublease to increase the space to 10,023 square feet. In October 2017, the Company entered into an amendment to its lease with Freescale in Chandler, Arizona to add 17,951 square feet of office space. The initial term of this amendment to the lease ends on January 31, 2022, with an option to renew the lease through August 31, 2024. The amendment provides the Company with 11 months free rent for the additional space of 17,951 square feet. The Company subsequently moved its headquarters into this new office space in December 2017.

The Company has another operating lease for its Arizona manufacturing facility lease, as amended, for certain of the fabrication, laboratory and office premises of Freescale, a related party. This lease is cancellable upon 24 months’ notice by either of the parties. In March 2017, the Company amended the premises covered to remove laboratory space, decrease fabrication space and expand office space. In October 2017, the Company extended the lease through January 31, 2020, which can be further extended through January 31, 2021 if an option to extend is initiated by Freescale.

The following is a schedule of minimum rental commitments under the Company’s operating leases at December 31, 2017 (in thousands):


Year Ending December 31,	Amount
2018	$	1,536
2019		1,645
2020		833
2021		766
2022		46
Total minimum lease payments	$	4,826

Total rent expense was $1.4 million, $1.5 million and $1.4 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Legal Proceedings

From time to time, the Company may become involved in legal proceedings arising from the ordinary course of its business. Management is currently not aware of any matters that will have a material adverse effect on the financial position, results of operations or cash flows of the Company.

Indemnifications

In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance.

Debt and Related Warrants

12 Months Ended

Dec. 31, 2017

Debt and Related Warrants

Debt and Related Warrants

5. Debt and Related Warrants

Prior Facilities

In June 2015, the Company executed a Loan and Security Agreement with Ares Venture Finance (2015 Credit Facility) comprising an $8.0 million term loan and a $4.0 million revolving loan. The term loan provides for interest at a floating rate equal to the greater of (a) 8.75% or (b) LIBOR plus 7.75% and has a term of four years. The term loan is payable in 15 monthly installments of interest only and 33 payments of principal and interest with an end-of-term fee of $180,000 due upon maturity. The revolving loan provides for interest at a floating rate equal to the prime rate plus 3.75% and has a term of two years. The Company may draw upon the loan facility for working capital purposes as required depending upon accounts receivable balances and other required conditions. In January 2016, the Company borrowed $1.5 million from the revolving loan.

Security for the 2015 Credit Facility includes all of the Company’s assets except for leased equipment. The 2015 Credit Facility contains customary covenants restricting the Company’s activities, including limitations on its ability to sell assets, engage in mergers and acquisitions, enter into transactions involving related parties, incur indebtedness or grant liens or negative pledges on its assets, make loans or make other investments. Under these covenants, the Company is prohibited from paying dividends with respect to its capital stock. The Company was in compliance with all covenants at December 31, 2016.

In April 2017, the Company repaid the outstanding balance of $1.1 million on the revolving loan at which time the unamortized balance of the debt discount of $10,000 was recognized as a loss on extinguishment of debt. In May 2017, the Company repaid the outstanding principal balance of $6.2 million on the term loan at which time the unamortized balance of the debt discount was $175,000, and paid a prepayment penalty of $61,000. The unamortized debt discount balance and the prepayment penalty were recognized as a loss on extinguishment of debt in the statements of operations and comprehensive loss.

2017 Credit Facility

On May 4, 2017, the Company entered into a Loan and Security Agreement with Silicon Valley Bank (2017 Credit Facility) for a $12.0 million term loan. The term loan provides for interest at a floating rate equal to the prime rate minus 0.75%. As of December 31, 2017, the interest rate was 3.75%. The term loan provides for a period of interest-only payments through April 30, 2018, followed by fixed principal and interest payments based on either a 24-month amortization schedule or a 36-month amortization schedule if the Company meets certain sales milestones. As of December 31, 2017, the Company determined it would not meet the sales milestones and as such the term loan will be based on a 24-month amortization schedule. Borrowings under the 2017 Credit Facility mature in May 2020. The Company is required to comply with certain covenants under the 2017 Credit Facility, including requirements to maintain a minimum liquidity ratio, meet certain revenue targets, and restrictions on certain actions without the consent of the lender, such as the disposal and acquisition of its business or property, changes in business, and mergers or acquisitions. An end of term fee of 6% of the amount borrowed must be made when the loan is prepaid or repaid, whether at maturity or as a result of a prepayment or acceleration or otherwise. The additional payment is being accreted using the effective interest method.

Security for the 2017 Credit Facility includes all of the Company’s assets except for intellectual property. The 2017 Credit Facility contains customary covenants restricting the Company’s activities, including limitations on its ability to sell assets, engage in mergers and acquisitions, enter into transactions involving related parties, incur indebtedness or grant liens or negative pledges on its assets, make loans or make other investments. Under these covenants, the Company is prohibited from paying dividends with respect to its capital stock. The Company was in compliance with all covenants at December 31, 2017. The 2017 Credit Facility contains a material adverse effect clause which provides that an event of default will occur if, among other triggers, an event occurs that could reasonably be expected to result in a material adverse effect on the Company’s business, operations or condition, or on the Company’s ability to perform its obligations under the term loan. As of December 31, 2017, management does not believe that it is probable that the clause will be triggered within the next twelve months, and therefore the term loan is classified as long-term.

The carrying value of the Company’s 2017 Credit Facility at December 31, 2017, was as follows (in thousands):


	Current		Long-Term
	Portion		debt		Total
Debt, including end of term fee	$	4,000	$	8,720	$	12,720
Less:
Discount attributable to end of term fee and debt issuance costs		(23)		(563)		(586)
Net carrying value of debt	$	3,977	$	8,157	$	12,134

The carrying value of the Company’s Prior Facilities at December 31, 2016, was as follows (in thousands):


	Current		Long-Term
	Portion		debt		Total
Debt, including end of term fee	$	4,054	$	4,301	$	8,355
Less:
Discount attributable to warrants, end of term fee and debt issuance cost		(177)		(83)		(260)
Net carrying value of debt	$	3,877	$	4,218	$	8,095

The table below shows the principal repayments due under the 2017 Credit Facility as of December 31, 2017 (in thousands):


	Principal Repayment
	as of December 31,
2018	$	4,000
2019		6,000
2020		2,720
Total principal repayments	$	12,720

Capital Lease Obligations

The Company leases certain equipment under capital lease obligations expiring in October 2020. The balance of the capital lease obligations was $31,000 and $7,000 at December 31, 2017 and 2016, respectively.

Property and equipment under capital leases amounted to $31,000 and $440,000 at December 31, 2017 and 2016, respectively. Accumulated depreciation and amortization on these assets was $2,000 and $433,000 at December 31, 2017 and 2016, respectively.

Future minimum rental commitments under the Company’s capital lease obligations are $11,000, $10,000, and $10,000 for the years ended December 31, 2018, 2019, and 2020, respectively.

Stockholders’ Equity

12 Months Ended

Dec. 31, 2017

Stockholders’ Equity

Stockholders’ Equity

6. Stockholders’ Equity

Common Stock

Common stockholders are entitled to dividends if and when declared by the board of directors. As of December 31, 2017, no dividends on common stock had been declared by the board of directors.

The Company had reserved shares of common stock for future issuance as follows:


	December 31,
	2017	2016
Options issued and outstanding	1,593,195	1,414,730
Shares available for future option grants	83,929	342,500
Common stock warrants	27,690	27,690
Total	1,704,814	1,784,920

Warrants

In connection with a credit facility, the Company issued to Silicon Valley Bank a warrant to purchase 3,076 shares of the Company’s Series A redeemable convertible preferred stock at an exercise price of $26.00 per share. The warrant could be exercised at any time and would expire, if not exercised, on December 14, 2019. At the date of issuance, the Company recorded the warrant as a debt discount of $63,000 and as a liability on the balance sheet at its fair value. At the date of the IPO of the Company’s common stock, the warrant was converted into a warrant to purchase 3,076 shares of the Company’s common stock. The warrant was remeasured to its fair value of $1,600 and the carrying value of the warrant of $1,600 was reclassified to additional paid in capital during the year ended December 31, 2016.

In connection with a credit facility, the Company issued to Silicon Valley Bank a warrant to purchase 6,153 shares of the Company’s Series B redeemable convertible preferred stock at an exercise price of $26.00 per share. The warrant can be exercised at any time and expires 10 years after the date of issuance. The Company recorded the warrant as a debt discount and as a liability on the balance sheet at its fair value of $106,000 on the date of issuance using the Black-Scholes option-pricing model. At the date of the IPO of the Company’s common stock, the warrant was converted into a warrant to purchase 6,153 shares of the Company’s common stock. The warrant was remeasured to its fair value of $14,900 and carrying value of the warrant of $14,900 was reclassified to additional paid in capital during the year ended December 31, 2016.

In connection with the 2015 Credit Facility, the Company issued to Ares Venture Finance a warrant to purchase 18,461 shares of the Company’s Series B redeemable convertible preferred stock at an exercise price of $26.00 per share. The warrant can be exercised at any time and expires 10 years after the date of issuance. The Company recorded the warrant as a debt discount and as a liability on the balance sheet at its fair value of $307,000 on the date of issuance using the Black-Scholes option-pricing model. At the date of the IPO of the Company’s common stock, the warrant was converted into a warrant to purchase 18,461 shares of the Company’s common stock. The warrant was remeasured to its fair value of $48,900 and the carrying value of the warrant of $48,900 was reclassified to additional paid-in capital during the year ended December 31, 2016.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Stock-Based Compensation

Stock-Based Compensation

7. Stock-Based Compensation

2016 Employee Incentive Plan

The Company’s board of directors adopted the 2016 Equity Incentive Plan (the 2016 Plan) on April 25, 2016, which was subsequently approved on September 20, 2016 by the Company’s stockholders. The 2016 Plan became effective on October 7, 2016, the date the Company’s registration statement was declared effective by the SEC.

The Company’s 2016 Plan provides for the grant of incentive stock options (ISOs), nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards, and other forms of equity compensation to employees, directors and consultants. In addition, the Company’s 2016 Plan provides for the grant of performance cash awards to employees, directors and consultants.

The maximum number of shares of common stock that may be issued under the Company’s 2016 Plan is 500,000 subject to an automatic increase on January 1 of each year, beginning on January 1, 2017, and continuing through and including January 1, 2026, by 3% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s board of directors.

2008 Employee Incentive Plan

The 2008 Equity Incentive Plan (the 2008 Plan) provided for the issuance of incentive stock options (ISO), nonqualified stock options, and other stock compensation awards. Under the terms of the 2008 Plan, the exercise price of an ISO shall be not less than 100% of the fair value of the stock at the date of grant, as determined by the board of directors, or in the case of certain ISOs, at 110% of the fair market value at the date of grant.

The term and vesting periods for options granted under the 2008 Plan were determined by the Company’s board of directors. Options granted generally vest over four years. Options must be exercised within a 10‑year period or sooner if so specified within the option agreement.

No further grants will be made under the Company’s 2008 Plan. However, any outstanding stock awards granted under the 2008 Plan will remain outstanding, subject to the terms of the Company’s 2008 Plan and the applicable stock award agreements, until such outstanding stock awards that are stock options are exercised or until they terminate or expire by their terms, or until such stock awards are fully settled, terminated or forfeited. At December 31, 2017, 826,258 options under the 2008 Plan remained outstanding.

Summary of Stock Option Activity

The following table summarizes the stock option activity for all grants under the 2008 Plan and 2016 Plan:


		Options Outstanding
			Weighted-		Weighted-
			Average		Average
	Options		Exercise		Remaining	Aggregate
	Available for	Number of	Price Per		Contractual	Intrinsic
	Grant	Options	Share		Life (years)	Value
						(In thousands)
Balance—December 31, 2015	55,330	927,175	$	4.43	7.3	$	6,500
Options authorized	785,364	—
Options granted	(563,523)	563,523		13.20
Options exercised	—	(10,639)		4.43		$	114
Options cancelled/forfeited	65,329	(65,329)		4.71
Balance—December 31, 2016	342,500	1,414,730	$	5.28	7.6	$	4,267
Options authorized	374,944	—
RSUs granted	(30,680)	—
Options granted	(757,900)	757,900		13.02
Options exercised	—	(281,483)		4.75		$	2,101
Options cancelled/forfeited	155,065	(297,952)		6.13
Balance—December 31, 2017	83,929	1,593,195		8.88	6.6	$	1,997
Options exercisable—December 31, 2017		766,233		5.43	3.7	$	1,825
Options vested and expected to vest—December 31, 2017		1,593,195		8.88	6.6	$	1,997

During the years ended December 31, 2017, 2016, and, 2015, the Company granted options with a weighted-average grant date fair value of $6.48, $4.52 and $4.42 per share, respectively.

The total fair value of options vested during the year was $1.5 million, $622,000, and $353,000 for the years ended December 31, 2017, 2016, and, 2015, respectively.

2016 Employee Stock Purchase Plan

The Company’s board of directors adopted the 2016 Employee Stock Purchase Plan (the ESPP) on April 25, 2016, which was subsequently approved on September 20, 2016 by the Company’s stockholders. The purpose of the ESPP is to secure the services of new employees, to retain the services of existing employees and to provide incentives for such individuals to exert maximum efforts toward the Company’s success and that of the Company’s affiliates. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Code. The board of directors, or a duly authorized committee thereof, will administer the Company’s ESPP.

The maximum aggregate number of shares of common stock that may be issued pursuant to the exercise of purchase rights under the Company’s ESPP that are granted to employees or to employees of any of the Company’s designated affiliates is 96,153 shares, subject to annual increases. The number of shares of common stock reserved for issuance under the Company’s ESPP will increase automatically each year, beginning on January 1, 2017, and continuing through and including January 1, 2026, by 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number as determined by the board of directors. In 2017, there was an increase of 124,981 shares reserved for issuance under the Company’s ESPP due to this provision. Shares subject to purchase rights granted under the Company’s ESPP that terminate without having been exercised in full will not reduce the number of shares available for issuance under the Company’s ESPP. The initial offering period (Initial Offering) under the ESPP began on October 7, 2016 and ended on October 12, 2017. The first purchase period under the 2016 ESPP commenced on October 12, 2016 and ended on April 12, 2017. The second purchase period under the Initial Offering began on April 13, 2017 and ended on October 12, 2017. The second offering period (Second Offering) under the ESPP began on October 13, 2017 and will end on October 12, 2018. The first purchase of the Second Offering period began on October 13, 2017 and will end on April 12, 2018. After the Second Offering, a new offering will begin every six months. Each offering under the ESPP will consist of two purchase periods of approximately six months in duration and will run concurrently. The Company had 183,544 shares available for issuance under the Company’s ESPP as of December 31, 2017. Employees purchased 37,590 shares for $256,000 during the year ended December 31, 2017.

The following table summarizes the assumptions used in the Black-Scholes option-pricing model to determine fair value of the Company’s common shares issued under the ESPP:


	Year Ended December 31,
	2017		2016		2015
Expected volatility	49.3 – 72.7	%	—	%	—	%
Risk-free interest rate	0.49 – 1.02	%	—	%	—	%
Expected term (in years)	0.5 – 1.0		—		—
Dividend yield	—	%	—	%	—	%

Modification of Stock Awards

In August 2017, the Company entered into a Separation Agreement with its former Chief Executive Officer which resulted in the acceleration in the vesting of certain unvested stock options as well as the extension of the exercise period for all vested options. As a result of the modification, the Company recorded stock-based compensation expense of $310,000 during the year ended December 31, 2017 to reflect the revised service period for the stock options and related vesting of shares that would otherwise not have vested.

In December 2016, the Company modified the terms of 396,028 vested and unvested stock option awards, affecting 77 employees, by reducing their exercise price from $15.86 per share to $6.63 per share. There was no change to any of the other terms of the option awards. The modification resulted in an incremental value of $629,000 being allocated to the options, of which $140,000 was recognized to expense immediately based on options that were vested at the time of the modification. The remaining incremental value of $489,000 attributable to unvested options is being recognized over their remaining vesting term.

Restricted of Stock Units

In September 2017, the Company’s board of directors authorized the issuance of Restricted Stock Units (RSUs), under the 2016 Plan and adopted a form of Restricted Stock Unit Award Agreement, which is intended to serve as a standard form agreement for RSU grants issued to employees, executive officers, directors and consultants. The fair value of the RSUs is recognized as expense ratably over the vesting period, as determined by the board of directors on the date of grant.

The following table summarizes RSU activity for the year ended December 31, 2017:


	RSUs Outstanding
		Weighted-
		Average
	Number of	Exercise
	Restricted Stock	Price Per
	Units	Share
Balance—December 31, 2016	—	$	—
Granted	30,680		10.55
Balance—December 31, 2017	30,680	$	10.55

The fair value of RSUs is determined on the date of grant based on the market price of the Company’s common stock on that date. As of December 31, 2017, there was $260,000 of unrecognized stock-based compensation expense related to RSUs to be recognized over a weighted-average period of 2.5 years.

Stock-based Compensation Expense

The Company recognized stock-based compensation expense as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development	$	488	$	403	$	169
General and administrative		1,297		637		190
Sales and marketing		263		101		57
Total	$	2,048	$	1,141	$	416

As of December 31, 2017, there was $5.1 million of total unrecognized compensation expense related to unvested options which the Company expects recognize over a weighted-average period of 3.3 years.

Employee Stock-based Compensation

Stock-based compensation expense for employees was $2.0 million, $1.1 million, and $407,000 for the years ended December 31, 2017, 2016, and 2015, respectively.

The Company estimated the fair value of each option grant using the Black-Scholes option-pricing model. The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period of the awards. The fair value of employee stock options was estimated using the assumptions below. Each of these inputs is subjective and its determination generally requires significant judgment.


	Year Ended December 31,
	2017		2016		2015
Expected volatility	46.7 – 52.0	%	42.6 – 45.3	%	44.1 – 48.9	%
Risk-free interest rate	1.85 - 2.14	%	1.12 – 2.26	%	1.51 – 1.79	%
Expected term (in years)	5.3 – 6.1		4.8 – 6.1		5.6 – 6.1
Dividend yield	—	%	—	%	—	%

Expected volatility. Since the Company does not have a long trading history for its common stock, the expected volatility was derived from the average historical volatilities of publicly traded companies within a similar industry that are considered to be comparable to the Company’s business over a period approximately equal to the expected term for employees’ options.

Risk-free interest rate. The risk-free interest rate is based on the U.S. Treasury yield with a maturity equal to the expected term of the option in effect at the time of grant.

Expected term. The expected term represents the period that the stock-based awards are expected to be outstanding. The Company used the simplified method to determine the expected term, which is calculated as the average of the time to vesting and the contractual life of the options.

Dividend yield. The Company has never paid dividends on its common stock and is prohibited from paying dividends on its common stock. Therefore, the Company used an expected dividend yield of zero.

Non-employee Stock-based Compensation

Stock-based compensation expense related to stock options granted to non-employees is recognized as the stock options vest. During the year ended December 31, 2017, the Company granted options to purchase 16,800 shares of common stock to non-employees with a weighted-average exercise price of $13.74 per share. During the year ended December 31, 2016, the Company granted options to purchase 8,073 shares of common stock to non-employees with a weighted-average exercise price of $7.51 per share. During the year ended December 31, 2015, the Company did not grant any options to non-employees.

Options to purchase 37,872 shares, 31,990 shares and 15,498 shares of common stock were outstanding with a weighted-average exercise price of $9.16, $5.26 and $4.42 per share as of December 31, 2017, 2016 and 2015, respectively. Stock-based compensation expense for non-employees was $69,000, $23,000, and $9,000 for the years ended December 31, 2017, 2016, and 2015, respectively.

The Company believes that the fair value of the stock options is more reliably measurable than the fair value of services received. The fair value of the stock options granted is calculated at each reporting date using the Black-Scholes option pricing model with the following assumptions:


	Year Ended December 31,
	2017		2016	2015
Expected volatility	46.7 – 60.5		52.3 – 52.7	51.6 – 52.9	%
Risk-free interest rate	2.09 – 2.44		1.94 – 2.41	1.72 – 2.02	%
Expected term (in years)	7.2 – 9.6		9.5 – 9.8	6.6 – 9.1
Dividend yield	—	%	—	—	%

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions
Related Party Transactions	9. Related Party Transactions Convertible Promissory Notes In January 2016, the Company entered into a Note Purchase Agreement with several of its stockholders for the issuance of convertible promissory notes (the 2016 Notes) for an aggregate amount of $5.0 million. The 2016 Notes bear interest at 5.0% per annum and have a maturity date of December 15, 2016, extended from the original maturity date of September 30, 2016. The outstanding principal amount and accrued interest on the 2016 Notes were convertible into shares of Series B redeemable convertible preferred stock, at any time, upon written election of the holders of at least a majority of the outstanding principal balance of the 2016 Notes. In the event of an equity financing with proceeds in excess of $5.0 million (Qualified Financing) prior to the maturity of the 2016 Notes, the outstanding principal and accrued interest convert into shares of stock issued in the equity financing based on a price per share equal to the price per share paid by investors in said financing. In the event of an IPO, the outstanding principal and accrued interest convert into shares of common stock at a price per share equal to 80% of the per share price of the common stock issued in the IPO. In the event of a deemed liquidation event occurring before the maturity date, the 2016 Notes will be repaid in cash in an amount equal to three times the outstanding principal amount. The redemption of the 2016 Notes upon a deemed liquidation event and in the event of an IPO were contingent redemption features that are not clearly and closely related to the debt instrument and thus were bifurcated and recognized as a derivative liability on the balance sheet at the date of issuance. The compound derivative was recorded as a debt discount at fair value of $653,000 on the issuance date of the 2016 Notes and was being amortized over the term of the 2016 Notes using the effective interest method. Upon the completion of the IPO, the outstanding principal balance of the 2016 Notes, including accrued interest of $176,000, was converted into 808,747 shares of common stock. Accordingly, the outstanding balance of the 2016 Notes of $5.2 million, the unamortized debt discount of $74,000 and the derivative liability of $70,000 were reclassified to additional paid-in capital. No gain or loss from the extinguishment of the debt was recognized in the statement of the operations as the holders of the 2016 Notes are related parties. In August 2016, the Company entered into a Note Purchase Agreement with existing stockholders for the issuance of subordinated convertible promissory notes (the 2016 Bridge Notes) for an aggregate principal amount of $3.5 million. The 2016 Bridge Notes bear interest at 5.0% per annum and have a maturity date of December 15, 2016, extended from the original maturity date of September 30, 2016. In the event of an equity financing with proceeds in excess of $5.0 million (Qualified Financing) prior to the maturity of the 2016 Bridge Notes, the outstanding principal and accrued interest convert into shares of stock issued in the Qualified Financing based on a price per share equal to the price per share paid by investors in such financing. In the event of an IPO, the outstanding principal and accrued interest convert into shares of common stock at a price per share equal to 80% of the per share price of the common stock issued in the IPO. In the event of a deemed liquidation event occurring before the maturity date, the 2016 Bridge Notes will be repaid in cash in an amount equal to three times the outstanding principal amount. The Company may not prepay the 2016 Bridge Notes without the consent of the Company and the majority holders of the outstanding balance of the promissory notes. The redemption of the 2016 Bridge Notes upon a deemed liquidation event and in the event of an IPO are contingent redemption features that are not clearly and closely related to the debt instrument and thus were bifurcated and recognized as a derivative liability on the balance sheet at the date of issuance. The compound derivative was recorded as a debt discount at fair value of $264,000 on the issuance date of the 2016 Bridge Notes and was being amortized over the term of the 2016 Bridge Notes using the effective interest method. Upon completion of the IPO, the outstanding principal balance of the 2016 Bridge Notes, including accrued interest of $35,000, was converted into 552,262 shares of common stock. Accordingly, the carrying value of the 2016 Bridge Notes of $3.5 million, the unamortized debt discount of $122,000 and the derivative liability of $50,000 were reclassified to additional paid-in capital. No gain or loss from the extinguishment of the debt was recognized in the statement of the operations as the holders of the 2016 Bridge Notes are related parties. Joint Development Agreement—GLOBALFOUNDRIES On October 17, 2014, the Company entered into a Joint Development Agreement (JDA) with GLOBALFOUNDRIES, Inc. (GF), a related party due to its equity ownership in the Company, for the joint development of the Company’s Spin Transfer Torque MRAM (STT-MRAM) technology. The term of the agreement is the later of four years from the effective date or until the completion, termination or expiration of the last statement of work entered into pursuant to the JDA. The JDA also states that the specific terms and conditions for the production and supply of the developed STT-MRAM technology would be pursuant to a separate manufacturing agreement entered into between the parties. Under the JDA, each party licenses its relevant intellectual property to the other party. For certain jointly developed works, the parties have agreed to follow an invention allocation procedure to determine ownership. In addition, GF possesses the exclusive right to manufacture the Company’s discrete and embedded STT-MRAM devices developed pursuant to the agreement until the earlier of three years after the qualification of the MRAM device for a particular technology node or four years after the completion of the relevant statement of work under which the device was developed. For the same exclusivity period associated with the relevant device, GF agreed not to license intellectual property developed in connection with the JDA to named competitors of the Company. Generally, unless otherwise specified in the agreement or a statement of work, the Company and GF share project costs, which do not include personnel or production qualification costs, equally under the JDA. If GF manufactures, sells or transfers to customers wafers containing production quantified STT-MRAM devices that utilize certain design information, GF will be required to pay the Company a royalty. The term of the agreement is four years and is extended until the completion of any development work, if later. In May 2016, the Company entered into an amendment to the JDA to modify the payment schedule and clarify its payment obligations for certain past project costs. Under the amendment, GF had the right to terminate the JDA if the Company did not pay the past project costs, with interest, by December 15, 2016. Such project costs were paid in December 2016. As of December 31, 2017, $25,000 was receivable from GF. There were no amounts receivable from GF as of December 31, 2016. As of December 31, 2017 and 2016, $749,000 and $979,000, respectively, were payable to GF for the Company’s share of the project costs under the JDA. During the year ended December 31, 2017, the Company purchased research and development equipment from GF for $747,000, which were included in property and equipment, net as of December 31, 2017. There were no such purchases from GF during the year ended December 31, 2016. The Company incurred project costs, recognized as research and development expense, of $5.2 million, $2.9 million, and $3.6 million during the years ended December 31, 2017, 2016, and 2015, respectively. The Company entered into a Statement of Work #4B (the SOW 4B) under the JDA with GF effective August 31, 2016. Under SOW 4B, the Company will collaborate with GF in planning, designing and supporting evaluation of 22nm embedded MRAM arrays. The Company is eligible to receive three substantive milestone payments from this collaboration: (a) $569,000 was due upon the delivery of the Company’s database of bias system schematics; (b) $650,000 was due upon the delivery of a Graphic Design Database System package; and (c) $406,000 is due upon demonstration that the embedded MRAM array meets the specifications agreed upon by the two parties. All the milestones were achieved in 2017 for which the Company recognized revenue of $1.6 million from GF in the year ended December 31, 2017. There was no revenue from GF for the years ended December 31, 2016 and 2015. On October 21, 2014, GF participated, along with other investors, in the Company’s Series B redeemable convertible preferred stock financing and purchased 192,307 shares at $26.00 per share. Contemporaneously, the Company sold 461,538 shares of its common stock to GF at a discounted price of $0.00026 per share. The common shares vest upon the achievement of a goal as set forth in the Statement of Work #1 (the “SOW”) under the JDA. The unvested common shares are subject to repurchase by the Company, if the JDA is terminated for any reason, for a one-year period after such termination, at a price that is the lower of the original price paid by GF or the fair value of the Company’s common stock as of the date of repurchase. The Company has determined that the issuance of these shares of common stock to GF represents compensation for services to be provided under the JDA. Accordingly, the shares are accounted for similar to a stock award granted to a non-employee of the Company and are remeasured to their fair value as they vest. Although the shares issued do not commence vesting until the achievement of the product qualification (the Initial Measurement Date), the Company has deemed it probable that the qualification requirement will be met and compensation expense related to the shares issued is being recognized prior to the Initial Measurement Date. Due to the vesting conditions, there will be multiple measurement dates, occurring on the Initial Measurement Date and at the end of each month thereafter. The fair value of vesting shares is effectively fixed at each measurement date while the fair value of the remaining unvested shares will be remeasured each subsequent measurement date until the shares are fully vested. During the year ended December 31, 2016, GF achieved the product qualification as set forth under the SOW. As such, a total of 211,538 shares of common stock became vested on August 21, 2016, the designated Initial Measurement Date. Subsequent to the Initial Measurement Date through December 31, 2017, an additional 153,846 shares of common stock became vested. As of December 31, 2017, there were 96,153 shares unvested that were subject to repurchase. During the years ended December 31, 2017, 2016, and 2015, the Company recognized non-cash compensation expense of $1.5 million, $965,000, and $1.8 million, respectively, in research and development expense, related to the vesting of the shares of common stock. The Company recognizes compensation expense based on the fair value of the common stock at each reporting period, which was $7.50, $8.29, and $13.52 per share as of December 31, 2017, 2016, and 2015, respectively. The decrease in the fair value of the common stock during the year ended December 31, 2017 and 2016 resulted in a reversal of compensation expense previously recognized on the unvested shares. Transactions with Freescale The Company has entered into various transactions with Freescale (a wholly-owned subsidiary of NXP), a related party due to its equity ownership in the Company. The Company leases its manufacturing facility in Chandler, Arizona, from Freescale and total rent expense during the years ended December 31, 2017, 2016, and 2015 were $1.0 million, $1.1 million, and $1.0 million, respectively. Freescale also performs processing of the Company’s products in its facility which are capitalized as part of the cost of inventory. The total processing costs incurred by the Company were $3.1 million, $2.5 million, and $3.9 million, for the years ended December 31, 2017, 2016, and 2015, respectively. In addition, Freescale is one of the Company’s largest customers for the sale of embedded wafers, and total revenue from Freescale was $2.3 million, $2.4 million, and $3.5 million for the years ended December 31, 2017, 2016, and 2015, respectively. In the year ended December 31, 2017 and 2016, the Company purchased wafers for its Condor product from Freescale for $1.4 million and $904,000, respectively, of which $638,000 and $505,000 was included in inventory as of December 31, 2017 and 2016, respectively. Amounts due from Freescale were $587,000 and $486,000 at December 31, 2017 and 2016, respectively. Amounts due to Freescale were $945,000 and $380,000 at December 31, 2017 and 2016, respectively.

Geographic Information

12 Months Ended

Dec. 31, 2017

Geographic Information

Geographic Information

10. Geographic Information

Revenue from customers is designated based on the geographic region or country to which the product is delivered or licensee is located. Revenue by country was as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
United States	$	4,759	$	4,321	$	5,362
Singapore		8,067		5,467		4,614
Japan		4,128		3,285		2,280
Germany		2,964		3,013		3,546
Taiwan		2,076		2,161		3,759
Hong Kong		2,179		2,122		2,744
All other		11,763		6,725		4,241
Total revenue	$	35,936	$	27,094	$	26,546

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

Income Taxes

11. Income Taxes

For the years ended December 31, 2017, 2016 and 2015, the Company recorded no provision for income taxes primarily due to losses incurred. The Company has incurred net operating losses for all the periods presented. The Company has not reflected any benefit of the net operating loss carryforwards in the accompanying financial statements. The Company has established a full valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets.

The reconciliation of the statutory federal income tax rate to the Company’s effective tax rate is as follows:


	Year Ended December 31,
	2017		2016		2015
Tax at statutory federal rate	(34.0)	%	(34.0)	%	(34.0)	%
State taxes, net of federal benefit	(1.4)		(1.5)		(1.9)
Stock-based compensation	(0.8)		1.3		0.8
Nondeductible fair value adjustment	—		(2.5)		—
Nondeductible interest	—		2.0		—
Change in valuation allowance	(34.2)		33.3		34.3
Federal tax rate change	70.2		—		—
Other	0.2		1.4		0.8
Provision for income taxes	(0.0)	%	(0.0)	%	(0.0)	%

The tax effects of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands):


	December 31,
	2017		2016
Deferred tax assets:
Net operating loss carryforwards	$	22,586	$	29,469
Inventory		1,520		1,187
Accruals		401		902
Depreciation and amortization		60		105
Other		1,228		1,312
Gross deferred tax assets		25,795		32,975
Valuation allowance		(25,721)		(32,850)
Deferred tax assets		74		125
Deferred tax liabilities:
Prepaid expenses		(74)		(125)
Deferred tax liabilities		(74)		(125)
Net deferred tax assets	$	—	$	—

The Company is required to reduce its deferred tax assets by a valuation allowance if it is more likely than not that some or all of its deferred tax assets will not be realized. Management must use judgment in assessing the potential need for a valuation allowance, which requires an evaluation of both negative and positive evidence. The weight given to the potential effect of negative and positive evidence should be commensurate with the extent to which it can be objectively verified. In determining the need for and amount of the valuation allowance, if any, the Company assesses the likelihood that it will be able to recover its deferred tax assets using historical levels of income, estimates of future income and tax planning strategies. As a result of historical cumulative losses, the Company determined that, based on all available evidence, there was substantial uncertainty as to whether it will recover recorded net deferred taxes in future periods. Accordingly, the Company recorded a valuation allowance against all of its net deferred tax assets as of December 31, 2017 and 2016. The net valuation allowance decreased by $7.1 million in 2017 and increased $5.3 million in 2016.

As of December 31, 2017, the Company had federal net operating loss carryforwards of approximately $100.1 million which will begin to expire in the year of 2028 if not utilized. In addition, the Company had state net operating loss carryforwards of approximately $39.3 million, which will begin to expire in 2023 if not utilized.

The Tax Reform Act of 1986 (the Act) provides for a limitation on the annual use of net operating loss and research and development tax credit carryforwards following certain ownership changes (as defined by the Act) that could limit the Company’s ability to utilize these carryforwards.

The Company files income tax returns in the U.S. federal and various state jurisdictions. The Company is subject to U.S. federal and state income tax examinations by authorities for all tax years due to the accumulated net operating losses that are being carried forward for tax purposes.

The Company has not identified any unrecognized tax benefits as of December 31, 2017 and 2016. As the Company has a full valuation allowance on its deferred tax assets, any unrecognized tax benefits would reduce the deferred tax assets and the valuation allowance in the same amount. The Company does not expect the amount of unrecognized tax benefits to materially change in the next twelve months.

On December 22, 2017, President Trump signed into law the 2017 Tax Act, which significantly amends the Internal Revenue Code of 1986. The 2017 Tax Act, among other things, reduces the corporate tax rate from a top marginal rate of 35% to a flat rate of 21%, limits the tax deduction for interest expense to 30% of adjusted earnings, eliminates net operating loss carrybacks, imposes a one-time tax on offshore earnings at reduced rates regardless of whether they are repatriated, allows immediate deductions for certain new investments instead of deductions for depreciation expense over time, and modifies or repeals many business deductions and credits. The rate reduction will take effect on January 1, 2018. The Company reviewed and incorporated the impact of the 2017 Tax Act in its tax calculations and disclosures. The primary impact on the Company stems from the re-measurement of its deferred taxes at the new corporate tax rate of 21%, which reduced the Company's net deferred tax assets, before valuation allowance, by $14.8 million. Due to the full valuation allowance, the change in deferred taxes was fully offset by the change in valuation allowance. The net effect of the tax reform enactment on the financial statements is $0 as of December 31, 2017. The Company continues to examine the impact these changes may have on the business.

Net Loss Per Share

12 Months Ended

Dec. 31, 2017

Net Loss Per Share

Net Loss Per Share

12. Net Loss Per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts):


		Year Ended December 31,
	2017			2016		2015
Numerator:
Net loss	$		(21,100)	$	(16,708)	$	(18,183)
Denominator:
Weighted-average common shares outstanding			12,640,094		5,117,226		3,013,743
Less: weighted-average unvested common shares subjected to repurchase			(155,110)		(378,730)		(461,538)
Weighted-average common shares outstanding used to calculate net loss per common share, basic and diluted			12,484,984		4,738,496		2,552,205
Net loss per common share, basic and diluted	$		(1.69)	$	(3.53)	$	(7.12)

The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per common share for the periods presented, because their inclusion would be anti-dilutive:


	Year Ended December 31,
	2017	2016	2015
Redeemable convertible preferred stock on an as-converted basis	—	—	2,486,199
Options to purchase common stock	1,593,195	1,414,730	927,175
Restricted stock units	30,680	—	—
Common stock subject to repurchase	96,153	211,538	461,538
Redeemable convertible preferred stock warrants on an as-converted basis	—	—	27,690
Common stock warrants	27,690	27,690	—
Total	1,747,718	1,653,958	3,902,602

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Selected Quarterly Financial Data (Unaudited)

Selected Quarterly Financial Data (Unaudited)

13. Selected Quarterly Financial Data (Unaudited)

Selected quarterly financial results from operations for the years ended December 31, 2017 and 2016 were as follows (in thousands, except per share amounts):


	Quarter Ended
	March 31,		June 30,		September 30,		December 31,
	2017		2017		2017		2017
Total revenue	$	7,880	$	8,925	$	9,008	$	10,123
Gross profit		4,217		5,792		5,255		6,221
Net loss		(6,086)		(5,187)		(5,446)		(4,381)
Net loss per common share, basic and diluted		(0.49)		(0.42)		(0.43)		(0.35)

	Quarter Ended
	March 31,		June 30,		September 30,		December 31,
	2016		2016		2016		2016
Total revenue	$	6,207	$	6,659	$	7,164	$	7,064
Gross profit		3,662		3,500		4,305		3,232
Net loss		(4,540)		(5,416)		(1,444)		(5,308)
Net loss per common share, basic and diluted		(1.78)		(2.12)		(0.54)		(0.48)

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events
Subsequent Events	14. Subsequent Events In February 2018 the Company completed a follow-on underwritten public offering of its common stock under its Registration Statement filed in November 2017 (File No. 333-221331), selling 3,772,447 shares of its common stock at an offering price of $7.00 per share for proceeds of $24.8 million, net of underwriting discounts and commissions, but before offering costs. In February 2018, the Company modified the terms of 400,000 vested and unvested stock option awards granted to the Chief Executive Officer, by reducing their exercise price from $16.25 per share to $7.64 per share. There was no change to any of the other terms of the option awards. The modification resulted in an incremental value of $600,000 being allocated to the options, of which $63,000 was recognized to expense immediately based on options that were vested at the time of the modification. The remaining incremental value of $537,000 attributable to unvested options will be recognized over the remaining vesting term.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies

Use of Estimates

Segments

Cash and Cash Equivalents

Accounts Receivable

Concentration of Credit Risk


	Revenue						Accounts Receivable
	Year Ended December 31,						December 31,
Customers	2017		2016		2015		2017		2016
Customer A	15	%	22	%	26	%	*	%	12	%
Customer B	*		*		13		15		13
Customer C	*		*		*		10		10
Customer D	16		12		*		*		18

*Less than 10%

Inventory

Fair Value of Financial Instruments

Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date.


	December 31, 2017
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	13,369	$	—	$	—	$	13,369
Total assets measured at fair value	$	13,369	$	—	$	—	$	13,369


	December 31, 2016
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	29,869	$	—	$	—	$	29,869
Total assets measured at fair value	$	29,869	$	—	$	—	$	29,869


	December 31,
	2017		2016		2015
Beginning balance	$	—	$	437	$	145
Issuance of redeemable convertible preferred stock warrants		—		—		307
Change in fair value recorded in other income, net		—		(372)		(15)
Reclassification to additional paid-in capital		—		(65)		—
Ending balance	$	—	$	—	$	437

The key assumptions used in the Black-Scholes option-pricing model for the valuation of the redeemable convertible preferred stock warrants were:


	Year Ended December 31,
	2017			2016			2015
Expected volatility		—	%		42.4 – 52.0	%		43.6 – 52.9	%
Risk-free interest rate		—	%		1.22 – 1.86	%		1.76 – 2.27	%
Expected term (in years)		—			4 – 9			5 – 10
Exercise price	$	—		$	26.00		$	26.00
Dividend yield		—	%		—	%		—	%

Property and Equipment


	Useful Lives
Computer and network equipment		2 years
Manufacturing equipment		2 – 7 years
Furniture and fixtures		7 years
Software		3 years

Impairment of Long-lived Assets

Intangible Assets

Redeemable Convertible Preferred Stock Warrant Liability

Revenue Recognition

Product Warranty

Research and Development

Stock-based Compensation

Income Taxes

Comprehensive Loss

Net Loss per Common Share

Recently Issued Pronouncements and Recently Adopted Pronouncements

Recently Issued Pronouncements

The Company plans to adopt ASU 2014-09 and its amendments on January 1, 2018 under the modified retrospective approach, applying the amendments to prospective reporting periods.

Recently Adopted Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Revenue and Accounts Receivable for Each Significant Customer


	Revenue						Accounts Receivable
	Year Ended December 31,						December 31,
Customers	2017		2016		2015		2017		2016
Customer A	15	%	22	%	26	%	*	%	12	%
Customer B	*		*		13		15		13
Customer C	*		*		*		10		10
Customer D	16		12		*		*		18

*Less than 10%

Schedule of Fair Value of Financial Assets Measured on Recurring Basis


	December 31, 2017
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	13,369	$	—	$	—	$	13,369
Total assets measured at fair value	$	13,369	$	—	$	—	$	13,369


	December 31, 2016
	Level 1		Level 2		Level 3			Total
Assets:
Money market funds	$	29,869	$	—	$	—	$	29,869
Total assets measured at fair value	$	29,869	$	—	$	—	$	29,869

Schedule of estimated useful lives of the assets


	Useful Lives
Computer and network equipment		2 years
Manufacturing equipment		2 – 7 years
Furniture and fixtures		7 years
Software		3 years

Redeemable Convertible Preferred Stock Warrants

Schedule of Change in Fair Value of Liability


	December 31,
	2017		2016		2015
Beginning balance	$	—	$	437	$	145
Issuance of redeemable convertible preferred stock warrants		—		—		307
Change in fair value recorded in other income, net		—		(372)		(15)
Reclassification to additional paid-in capital		—		(65)		—
Ending balance	$	—	$	—	$	437

Schedule of Assumptions Used in Valuation of Redeemable Convertible Preferred Stock Warrants


	Year Ended December 31,
	2017			2016			2015
Expected volatility		—	%		42.4 – 52.0	%		43.6 – 52.9	%
Risk-free interest rate		—	%		1.22 – 1.86	%		1.76 – 2.27	%
Expected term (in years)		—			4 – 9			5 – 10
Exercise price	$	—		$	26.00		$	26.00
Dividend yield		—	%		—	%		—	%

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2017

Balance Sheet Components

Schedule of Inventory

Inventory consisted of the following (in thousands):


	December 31,
	2017		2016
Raw materials	$	682	$	853
Work-in-process		4,517		3,152
Finished goods		4,638		1,064
Total inventory	$	9,837	$	5,069

Schedule of Property and equipment, net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2017		2016
Manufacturing equipment	$	10,465	$	8,983
Computer and network equipment		710		588
Furniture and fixtures		218		188
Software		455		333
Leasehold improvements		1,474		13
Total property and equipment, gross		13,322		10,105
Less: accumulated depreciation		(9,376)		(8,185)
Total property and equipment, net	$	3,946	$	1,920

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2017		2016
Accrued payroll-related expenses	$	1,331	$	1,045
Deferred licensing revenue		—		229
Deferred rent		230		248
Accrued sales commissions payable to sales representatives		75		193
Other		618		96
Total accrued liabilities	$	2,254	$	1,811

Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies

Schedule of minimum rental commitments under operating leases

The following is a schedule of minimum rental commitments under the Company’s operating leases at December 31, 2017 (in thousands):


Year Ending December 31,	Amount
2018	$	1,536
2019		1,645
2020		833
2021		766
2022		46
Total minimum lease payments	$	4,826

Debt and Related Warrants (Tables)

12 Months Ended

Dec. 31, 2017

Debt and Related Warrants

Summary of Debt

The carrying value of the Company’s 2017 Credit Facility at December 31, 2017, was as follows (in thousands):


	Current		Long-Term
	Portion		debt		Total
Debt, including end of term fee	$	4,000	$	8,720	$	12,720
Less:
Discount attributable to end of term fee and debt issuance costs		(23)		(563)		(586)
Net carrying value of debt	$	3,977	$	8,157	$	12,134

The carrying value of the Company’s Prior Facilities at December 31, 2016, was as follows (in thousands):


	Current		Long-Term
	Portion		debt		Total
Debt, including end of term fee	$	4,054	$	4,301	$	8,355
Less:
Discount attributable to warrants, end of term fee and debt issuance cost		(177)		(83)		(260)
Net carrying value of debt	$	3,877	$	4,218	$	8,095

Summary of Principal Repayments of 2015 Credit Facility

The table below shows the principal repayments due under the 2017 Credit Facility as of December 31, 2017 (in thousands):


	Principal Repayment
	as of December 31,
2018	$	4,000
2019		6,000
2020		2,720
Total principal repayments	$	12,720

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Stockholders’ Equity

Summary of Common Stock Reserved for Future Issuance


	December 31,
	2017	2016
Options issued and outstanding	1,593,195	1,414,730
Shares available for future option grants	83,929	342,500
Common stock warrants	27,690	27,690
Total	1,704,814	1,784,920

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Stock Option Activity


		Options Outstanding
			Weighted-		Weighted-
			Average		Average
	Options		Exercise		Remaining	Aggregate
	Available for	Number of	Price Per		Contractual	Intrinsic
	Grant	Options	Share		Life (years)	Value
						(In thousands)
Balance—December 31, 2015	55,330	927,175	$	4.43	7.3	$	6,500
Options authorized	785,364	—
Options granted	(563,523)	563,523		13.20
Options exercised	—	(10,639)		4.43		$	114
Options cancelled/forfeited	65,329	(65,329)		4.71
Balance—December 31, 2016	342,500	1,414,730	$	5.28	7.6	$	4,267
Options authorized	374,944	—
RSUs granted	(30,680)	—
Options granted	(757,900)	757,900		13.02
Options exercised	—	(281,483)		4.75		$	2,101
Options cancelled/forfeited	155,065	(297,952)		6.13
Balance—December 31, 2017	83,929	1,593,195		8.88	6.6	$	1,997
Options exercisable—December 31, 2017		766,233		5.43	3.7	$	1,825
Options vested and expected to vest—December 31, 2017		1,593,195		8.88	6.6	$	1,997

Schedule of Restricted Stock Unit Activity


	RSUs Outstanding
		Weighted-
		Average
	Number of	Exercise
	Restricted Stock	Price Per
	Units	Share
Balance—December 31, 2016	—	$	—
Granted	30,680		10.55
Balance—December 31, 2017	30,680	$	10.55

Summary of Stock-Based Compensation Expense

The Company recognized stock-based compensation expense as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development	$	488	$	403	$	169
General and administrative		1,297		637		190
Sales and marketing		263		101		57
Total	$	2,048	$	1,141	$	416

2016 Employee Stock Purchase Plan

Schedule of Fair Value Assumptions


	Year Ended December 31,
	2017		2016		2015
Expected volatility	49.3 – 72.7	%	—	%	—	%
Risk-free interest rate	0.49 – 1.02	%	—	%	—	%
Expected term (in years)	0.5 – 1.0		—		—
Dividend yield	—	%	—	%	—	%

Employees

Schedule of Fair Value Assumptions


	Year Ended December 31,
	2017		2016		2015
Expected volatility	46.7 – 52.0	%	42.6 – 45.3	%	44.1 – 48.9	%
Risk-free interest rate	1.85 - 2.14	%	1.12 – 2.26	%	1.51 – 1.79	%
Expected term (in years)	5.3 – 6.1		4.8 – 6.1		5.6 – 6.1
Dividend yield	—	%	—	%	—	%

Non-Employee

Schedule of Fair Value Assumptions


	Year Ended December 31,
	2017		2016	2015
Expected volatility	46.7 – 60.5		52.3 – 52.7	51.6 – 52.9	%
Risk-free interest rate	2.09 – 2.44		1.94 – 2.41	1.72 – 2.02	%
Expected term (in years)	7.2 – 9.6		9.5 – 9.8	6.6 – 9.1
Dividend yield	—	%	—	—	%

Geographic Information (Tables)

12 Months Ended

Dec. 31, 2017

Geographic Information

Schedule of revenue by country

Revenue from customers is designated based on the geographic region or country to which the product is delivered or licensee is located. Revenue by country was as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
United States	$	4,759	$	4,321	$	5,362
Singapore		8,067		5,467		4,614
Japan		4,128		3,285		2,280
Germany		2,964		3,013		3,546
Taiwan		2,076		2,161		3,759
Hong Kong		2,179		2,122		2,744
All other		11,763		6,725		4,241
Total revenue	$	35,936	$	27,094	$	26,546

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of reconciliation of statutory federal income tax rate


	Year Ended December 31,
	2017		2016		2015
Tax at statutory federal rate	(34.0)	%	(34.0)	%	(34.0)	%
State taxes, net of federal benefit	(1.4)		(1.5)		(1.9)
Stock-based compensation	(0.8)		1.3		0.8
Nondeductible fair value adjustment	—		(2.5)		—
Nondeductible interest	—		2.0		—
Change in valuation allowance	(34.2)		33.3		34.3
Federal tax rate change	70.2		—		—
Other	0.2		1.4		0.8
Provision for income taxes	(0.0)	%	(0.0)	%	(0.0)	%

Schedule of tax effects of temporary differences and carryforwards

The tax effects of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands):


	December 31,
	2017		2016
Deferred tax assets:
Net operating loss carryforwards	$	22,586	$	29,469
Inventory		1,520		1,187
Accruals		401		902
Depreciation and amortization		60		105
Other		1,228		1,312
Gross deferred tax assets		25,795		32,975
Valuation allowance		(25,721)		(32,850)
Deferred tax assets		74		125
Deferred tax liabilities:
Prepaid expenses		(74)		(125)
Deferred tax liabilities		(74)		(125)
Net deferred tax assets	$	—	$	—

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Net Loss Per Share

Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts):


		Year Ended December 31,
	2017			2016		2015
Numerator:
Net loss	$		(21,100)	$	(16,708)	$	(18,183)
Denominator:
Weighted-average common shares outstanding			12,640,094		5,117,226		3,013,743
Less: weighted-average unvested common shares subjected to repurchase			(155,110)		(378,730)		(461,538)
Weighted-average common shares outstanding used to calculate net loss per common share, basic and diluted			12,484,984		4,738,496		2,552,205
Net loss per common share, basic and diluted	$		(1.69)	$	(3.53)	$	(7.12)

Schedule of Potentially Dilutive Securities Excluded from Diluted Net Loss Per Common Share


	Year Ended December 31,
	2017	2016	2015
Redeemable convertible preferred stock on an as-converted basis	—	—	2,486,199
Options to purchase common stock	1,593,195	1,414,730	927,175
Restricted stock units	30,680	—	—
Common stock subject to repurchase	96,153	211,538	461,538
Redeemable convertible preferred stock warrants on an as-converted basis	—	—	27,690
Common stock warrants	27,690	27,690	—
Total	1,747,718	1,653,958	3,902,602

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Selected Quarterly Financial Data (Unaudited)

Schedule of selected quarterly financial results from operations

Selected quarterly financial results from operations for the years ended December 31, 2017 and 2016 were as follows (in thousands, except per share amounts):


	Quarter Ended
	March 31,		June 30,		September 30,		December 31,
	2017		2017		2017		2017
Total revenue	$	7,880	$	8,925	$	9,008	$	10,123
Gross profit		4,217		5,792		5,255		6,221
Net loss		(6,086)		(5,187)		(5,446)		(4,381)
Net loss per common share, basic and diluted		(0.49)		(0.42)		(0.43)		(0.35)

	Quarter Ended
	March 31,		June 30,		September 30,		December 31,
	2016		2016		2016		2016
Total revenue	$	6,207	$	6,659	$	7,164	$	7,064
Gross profit		3,662		3,500		4,305		3,232
Net loss		(4,540)		(5,416)		(1,444)		(5,308)
Net loss per common share, basic and diluted		(1.78)		(2.12)		(0.54)		(0.48)

Organization and Operations (Details) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Oct. 07, 2016 $ / shares shares	Oct. 07, 2016 USD ($) $ / shares shares	Feb. 28, 2018 USD ($)	Sep. 30, 2016	Dec. 31, 2016 USD ($) shares
Organization And Operations
Reverse stock split ratio				0.038
Net proceeds from initial public offering					$ 33,864
Net proceeds from issuance of common stock in private placement					4,650
Convertible promissory notes payable
Organization And Operations
Conversion of convertible promissory notes to common stock (in shares) \| shares	1,361,009
Initial Public Offering
Organization And Operations
Issuance of Series B redeemable convertible stock (in shares) \| shares		5,000,000
Initial public offering price per share \| $ / shares	$ 8.00	$ 8.00
Net proceeds from initial public offering		$ 33,900
Proceeds, net of underwriting discounts and commissions, but before offering costs					33,864
Private Placement
Organization And Operations
Issuance of Series B redeemable convertible stock (in shares) \| shares		625,000
Net proceeds from issuance of common stock in private placement		$ 4,700
Proceeds, net of underwriting discounts and commissions, but before offering costs					$ 4,650
Follow-on offering
Organization And Operations
Proceeds, net of underwriting discounts and commissions, but before offering costs			$ 24,800
Redeemable Convertible Preferred Stock
Organization And Operations
Conversion of redeemable convertible preferred stock to common stock (in shares) \| shares	2,486,199				(2,486,199)

Summary of Significant Accounting Policies - Schedule of Revenue and Accounts Receivable for Each Significant Customer (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015
Segments
Number of operating segments \| segment	1
Allowance for Trade Receivables
Accounts Receivable
Accounts receivable allowance	$ 0	$ 0
Allowance for Product Returns
Accounts Receivable
Accounts receivable allowance	$ 147,000	$ 188,000
Revenue \| Customer Concentration Risk \| Customer A
Accounts Receivable
Concentration risk percentage	15.00%	22.00%	26.00%
Revenue \| Customer Concentration Risk \| Customer B
Accounts Receivable
Concentration risk percentage			13.00%
Revenue \| Customer Concentration Risk \| Customer B \| Maximum
Accounts Receivable
Concentration risk percentage	10.00%	10.00%
Revenue \| Customer Concentration Risk \| Customer C \| Maximum
Accounts Receivable
Concentration risk percentage	10.00%	10.00%	10.00%
Revenue \| Customer Concentration Risk \| Customer D
Accounts Receivable
Concentration risk percentage	16.00%	12.00%
Revenue \| Customer Concentration Risk \| Customer D \| Maximum
Accounts Receivable
Concentration risk percentage			10.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer A
Accounts Receivable
Concentration risk percentage		12.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer A \| Maximum
Accounts Receivable
Concentration risk percentage	10.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer B
Accounts Receivable
Concentration risk percentage	15.00%	13.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer C
Accounts Receivable
Concentration risk percentage	10.00%	10.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer D
Accounts Receivable
Concentration risk percentage		18.00%
Accounts Receivable, net \| Customer Concentration Risk \| Customer D \| Maximum
Accounts Receivable
Concentration risk percentage	10.00%

Summary of Significant Accounting Policies - Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value
Total assets measured at fair value	$ 13,369	$ 29,869
Level 1
Fair Value
Total assets measured at fair value	13,369	29,869
Money Market Funds
Fair Value
Money market funds	13,369	29,869
Money Market Funds \| Level 1
Fair Value
Money market funds	$ 13,369	$ 29,869

Summary of Significant Accounting Policies - Schedule of Change in Fair Value of Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Redeemable convertible preferred stock warrant
Reclassification to additional paid-in capital	$ 65
Redeemable Convertible Preferred Stock Warrants \| Level 3
Redeemable convertible preferred stock warrant
Beginning balance	437	$ 145
Issuance of redeemable convertible preferred stock warrants		307
Change in fair value recorded in other income, net	(372)	(15)
Reclassification to additional paid-in capital	$ (65)
Ending balance		$ 437

Summary of Significant Accounting Policies - Schedule of Assumptions Used in Valuation of Redeemable Convertible Preferred Stock Warrants (Details) - Redeemable Convertible Preferred Stock Warrants - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Measurements
Exercise price	$ 26.00	$ 26.00
Minimum
Fair Value Measurements
Expected volatility	42.40%	43.60%
Risk-free interest rate	1.22%	1.76%
Expected term (in years)	4 years	5 years
Maximum
Fair Value Measurements
Expected volatility	52.00%	52.90%
Risk-free interest rate	1.86%	2.27%
Expected term (in years)	9 years	10 years

Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Impairment of Long-lived Assets
Impairment of long-lived assets	$ 0	$ 0	$ 0
Computer and network equipment
Property and Equipment, Net
Useful Lives	2 years
Manufacturing equipment \| Minimum
Property and Equipment, Net
Useful Lives	2 years
Manufacturing equipment \| Maximum
Property and Equipment, Net
Useful Lives	7 years
Furniture and fixtures
Property and Equipment, Net
Useful Lives	7 years
Software
Property and Equipment, Net
Useful Lives	3 years

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration risk
Deferred revenue	$ 2,600,000	$ 2,900,000
Deferred cost of sales	900,000	1,100,000
Deferred income on shipments to distributors	1,720,000	1,827,000
Income Taxes
Interest and penalties on unrecognized tax benefits	0	0	$ 0
Recently Issued Pronouncement
Deferred income on shipments to distributors	1,720,000	$ 1,827,000
ASU 2014-09
Concentration risk
Deferred income on shipments to distributors	1,700,000
Recently Issued Pronouncement
Deferred income on shipments to distributors	1,700,000
ASU 2014-09 \| Minimum
Recently Issued Pronouncement
Concessions and price protection credits offered to distributors	200,000
ASU 2014-09 \| Maximum
Recently Issued Pronouncement
Concessions and price protection credits offered to distributors	$ 400,000

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory
Raw materials	$ 682	$ 853
Work-in-process	4,517	3,152
Finished goods	4,638	1,064
Total inventory	$ 9,837	$ 5,069

Balance Sheet Components - Property and Equipment Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment, Net
Total property and equipment, gross	$ 13,322	$ 10,105
Less: accumulated depreciation	(9,376)	(8,185)
Total property and equipment, net	3,946	1,920
Depreciation and amortization expense	1,200	700	$ 1,200
Manufacturing equipment
Property and Equipment, Net
Total property and equipment, gross	10,465	8,983
Computer and network equipment
Property and Equipment, Net
Total property and equipment, gross	710	588
Furniture and fixtures
Property and Equipment, Net
Total property and equipment, gross	218	188
Software
Property and Equipment, Net
Total property and equipment, gross	455	333
Leasehold improvements
Property and Equipment, Net
Total property and equipment, gross	$ 1,474	$ 13

Balance Sheet Components - Schedule of Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2008
Intangible assets, net
Acquired intangible assets				$ 910,000
Amortization of intangible assets		$ (910,000)
Amortization expense	$ 0	$ 132,000	$ 150,000

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued liabilities
Accrued payroll-related expenses	$ 1,331	$ 1,045
Deferred licensing revenue		229
Deferred rent	230	248
Accrued sales commissions payable to sales representatives	75	193
Other	618	96
Total accrued liabilities	$ 2,254	$ 1,811

Commitments and Contingencies (Details) $ in Thousands	1 Months Ended			12 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Oct. 31, 2017 ft²	Mar. 31, 2017 ft²	Jan. 31, 2017 ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Minimum rental commitments
2018				$ 1,536
2019				1,645
2020				833
2021				766
2022				46
Total minimum lease payments				4,826
Total rent expense				$ 1,400	$ 1,500	$ 1,400
Arizona manufacturing facility \| Freescale
Minimum rental commitments
Period to cancel lease upon notice				24 months
Office and Laboratory Space \| Freescale
Minimum rental commitments
Term of lease (in years)			5 years
Number of rent free months	11 months
Additional area of operating lease \| ft²	17,951	10,023	6,560

Debt and Related Warrants - Warrants - Additional Information (Details)	1 Months Ended
	May 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 31, 2016 USD ($)	Jun. 30, 2015 USD ($) installment payment	Dec. 31, 2010 USD ($)
Term Loan 2015 Credit Facility
Warrants
Loan agreement amount				$ 8,000,000
Debt instrument, interest rate				8.75%
Line of credit facility expiration period				4 years
Number of term loan installments \| installment				15
Number of interest and principal payments \| payment				33
Term loan end-of-term fee				$ 180,000
Repayment of credit facility	$ 6,200,000
Unamortized debt discount	175,000
Prepayment penalty	$ 61,000
Term Loan 2015 Credit Facility \| LIBOR
Warrants
Interest rate, basis spread percentage				7.75%
Term Loan 2015 Credit Facility \| Prime Rate
Warrants
Interest rate, basis spread percentage				3.75%
Revolving loan 2015 Credit Facility
Warrants
Loan agreement amount				$ 4,000,000
Line of credit facility expiration period				2 years
Proceeds from revolving loan			$ 1,500,000
Repayment of credit facility		$ 1,100,000
Unamortized debt discount		$ 10,000,000
Warrants to Purchase Series A Redeemable Convertible Preferred Stock \| SVB Credit Facility
Warrants
Debt discount					$ 63,000

Debt and Related Warrants - 2017 Facility - Additional Information (Details) - 2017 Credit Facility $ in Millions	May 04, 2017 USD ($) item
Debt
Loan agreement amount \| $	$ 12.0
End-of-term fee (as a percent)	6.00%
Prime Rate
Debt
Interest rate, negative basis spread percentage	0.75%
Interest rate	3.75%
Prime Rate \| Minimum
Debt
Number of interest and principal payments	24
Prime Rate \| Maximum
Debt
Number of interest and principal payments	36

Debt and Related Warrants - Carrying Value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt
Net carrying value of debt, Current Portion	$ 3,987	$ 3,884
Net carrying value of debt, Long-term debt	8,178	4,218
2017 Credit Facility
Debt
Debt, including end of term fee, Current Portion	4,000
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Current Portion	(23)
Net carrying value of debt, Current Portion	3,977
Debt, including end of term fee, Long-term debt	8,720
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Long-term debt	(563)
Net carrying value of debt, Long-term debt	8,157
Debt, including end of term fee, Total	12,720
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Total	(586)
Net carrying value of debt, Total	$ 12,134
2015 Credit Facility
Debt
Debt, including end of term fee, Current Portion		4,054
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Current Portion		(177)
Net carrying value of debt, Current Portion		3,877
Debt, including end of term fee, Long-term debt		4,301
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Long-term debt		(83)
Net carrying value of debt, Long-term debt		4,218
Debt, including end of term fee, Total		8,355
Less: Discount attributable to warrants, end of term fee and debt issuance costs, Total		(260)
Net carrying value of debt, Total		$ 8,095

Debt and Related Warrants - Summary of Principal Repayments of 2017 Credit Facility (Details) - 2017 Credit Facility $ in Thousands	Dec. 31, 2017 USD ($)
Debt
2018	$ 4,000
2019	6,000
2020	2,720
Total principal repayments	$ 12,720

Debt and Related Warrants - Capital Lease Obligations (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt and Related Warrants
Capital lease obligations future minimum lease payments	$ 31,000	$ 7,000
Property and equipment under capital leases	31,000	440,000
Capital lease obligations accumulated depreciation and amortization	2,000	$ 433,000
Future minimum rental commitments
2018	11,000,000
2019	10,000,000
2020	$ 10,000,000

Stockholders’ Equity - Summary of Common Stock Reserved for Future Issuance (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Common stock reserved
Dividends on common stock	$ 0.00
Reserved shares of common stock for future issuance	1,704,814	1,784,920
Common Stock Warrants
Common stock reserved
Reserved shares of common stock for future issuance	27,690	27,690
Options Issued and Outstanding
Common stock reserved
Reserved shares of common stock for future issuance	1,593,195	1,414,730
Shares Available for Future Option Grants
Common stock reserved
Reserved shares of common stock for future issuance	83,929	342,500

Stockholders’ Equity - Warrants (Details) - USD ($)	1 Months Ended		12 Months Ended
Stockholders’ Equity - Warrants (Details) - USD ($)	Jun. 30, 2015	Feb. 28, 2014	Dec. 31, 2016	Dec. 31, 2015	Oct. 07, 2016	Dec. 31, 2010
Warrants
Loss from remeasurement			$ (372,000)	$ (15,000)
Warrants to Purchase Series A Redeemable Convertible Preferred Stock \| SVB Credit Facility
Warrants
Number of shares the warrant can be converted to						3,076
Warrant exercise price						$ 26.00
Debt discount						$ 63,000
Fair Value Of Warrants			1,600
Additional paid in capital			1,600
Warrants to Purchase Series A Redeemable Convertible Preferred Stock \| SVB Credit Facility \| Common Stock
Warrants
Number of shares the warrant can be converted to					3,076
Warrants to Purchase Series B Redeemable Convertible Preferred Stock \| 2015 Credit Facility
Warrants
Number of shares the warrant can be converted to	18,461
Warrant exercise price	$ 26.00
Fair Value Of Warrants	$ 307,000		48,900
Warrant exercise expiration period	10 years
Additional paid in capital			48,900
Warrants to Purchase Series B Redeemable Convertible Preferred Stock \| 2015 Credit Facility \| Common Stock
Warrants
Number of shares the warrant can be converted to	18,461
Warrants to Purchase Series B Redeemable Convertible Preferred Stock \| SVB Credit Facility
Warrants
Number of shares the warrant can be converted to		6,153
Warrant exercise price		$ 26.00
Fair Value Of Warrants		$ 106,000	14,900
Warrant exercise expiration period		10 years
Additional paid in capital			$ 14,900
Warrants to Purchase Series B Redeemable Convertible Preferred Stock \| SVB Credit Facility \| Common Stock
Warrants
Number of shares the warrant can be converted to					6,153

Stock-Based Compensation - Additional Information (Details)			1 Months Ended	12 Months Ended
	Oct. 07, 2016 shares	Sep. 20, 2016 item shares	Dec. 31, 2016 USD ($) employee $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Nov. 30, 2016 $ / shares
Share-based Compensation
Shares available for future issuance (in shares)			342,500	83,929	342,500	55,330
Number of stock options granted				757,900	563,523
Options remained outstanding			1,414,730	1,593,195	1,414,730	927,175
Weighted-average grant date fair value of options granted \| $ / shares				$ 6.48	$ 4.52	$ 4.42
Total grant date fair value of options vested \| $				$ 1,500,000	$ 622,000	$ 353,000
Unrecognized compensation expense related to unvested options \| $				$ 5,100,000
Unrecognized compensation expense, weighted-average period expected to be recognized				3 years 3 months 18 days
Weighted-average exercise price (per share) \| $ / shares			$ 5.28	$ 8.88	$ 5.28	$ 4.43
Stock-based compensation expense \| $				$ 2,048,000	$ 1,141,000	$ 416,000
Former Chief Executive Officer \| Accelerated Vesting Due To Separation Agreement
Share-based Compensation
Stock-based compensation expense \| $				310,000
Employees
Share-based Compensation
Number of vested and unvested stock option award modified			396,028
Number of employees affected \| employee			77
Weighted-average exercise price (per share) \| $ / shares			$ 6.63		$ 6.63		$ 15.86
Stock-based compensation expense \| $				$ 2,000,000	$ 1,100,000	$ 407,000
Incremental modification value \| $			$ 629,000
Employees \| Immediate vesting
Share-based Compensation
Incremental modification value \| $			140,000
Employees \| Remaining vesting
Share-based Compensation
Incremental modification value \| $			$ 489,000
Non-Employee
Share-based Compensation
Number of stock options granted				16,800	8,073
Options remained outstanding			31,990	37,872	31,990	15,498
Weighted-average grant date fair value of options granted \| $ / shares				$ 13.74	$ 7.51
Weighted-average exercise price (per share) \| $ / shares			$ 5.26	$ 9.16	$ 5.26	$ 4.42
Stock-based compensation expense \| $				$ 69,000	$ 23,000	$ 9,000
2016 Employee Incentive Plan
Share-based Compensation
Maximum number of common stock shares may be issued under the plan	500,000
Annual increases in the number of shares available for issuance, percentage of outstanding capital stock	3.00%
2008 Equity Incentive Plan
Share-based Compensation
Vesting period				4 years
Exercise period				10 years
Options remained outstanding				826,258
2008 Equity Incentive Plan \| Incentive Stock Options \| Minimum
Share-based Compensation
Percentage of exercise price of fair market value of stock at the date of grant				100.00%
2008 Equity Incentive Plan \| Incentive Stock Options \| Maximum
Share-based Compensation
Percentage of exercise price of fair market value of stock at the date of grant				110.00%
2016 Employee Stock Purchase Plan
Share-based Compensation
Maximum number of common stock shares may be issued under the plan		96,153
Annual increases in the number of shares available for issuance, percentage of outstanding capital stock		1.00%
Increase in number of shares available for grant				124,981
Number of purchase periods \| item		2
Period difference for each offering		6 months
Length of time of purchase period (in months)		6 months
Shares available for future issuance (in shares)				183,544
Number of shares issued (in shares)				37,590
Value of share issued \| $				$ 256,000

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock-Based Compensation
Options Available for Grant, Outstanding, Beginning balance	342,500	55,330
Options Available for Grant, Options authorized	374,944	785,364
Options Available for Grant, RSUs granted	(30,680)
Options Available for Grant, Options granted	(757,900)	(563,523)
Options Available for Grant, Options cancelled/forfeited	155,065	65,329
Options Available for Grant, Outstanding, Ending balance	83,929	342,500	55,330
Number of Options, Outstanding, Beginning balance	1,414,730	927,175
Number of Options, Options granted	757,900	563,523
Number of Options, Options exercised	(281,483)	(10,639)
Number of Options, Options cancelled/forfeited	(297,952)	(65,329)
Number of Options, Outstanding, Ending balance	1,593,195	1,414,730	927,175
Number of Options, exercisable	766,233
Number of Options, vested and expected to vest	1,593,195
Weighted - Average Exercise Price Per Share, Options outstanding, Beginning balance	$ 5.28	$ 4.43
Weighted - Average Exercise Price Per Share, Options granted	13.02	13.20
Weighted - Average Exercise Price Per Share, Options exercised	4.75	4.43
Weighted - Average Exercise Price Per Share, Options cancelled/forfeited	6.13	4.71
Weighted - Average Exercise Price Per Share, Options outstanding, Ending balance	8.88	$ 5.28	$ 4.43
Weighted - Average Exercise Price Per Share, Options exercisable	5.43
Weighted - Average Exercise Price Per Share, Options vested and expected to vest	$ 8.88
Weighted - Average Remaining Contractual Life, Options outstanding	6 years 7 months 6 days	7 years 7 months 6 days	7 years 3 months 18 days
Weighted - Average Remaining Contractual Life, Options exercisable	3 years 8 months 12 days
Weighted - Average Remaining Contractual Life, Options vested and expected to vest	6 years 7 months 6 days
Aggregate Intrinsic Value, Options outstanding	$ 1,997	$ 4,267	$ 6,500
Aggregate Intrinsic Value, Options exercised	2,101	$ 114
Aggregate Intrinsic Value, Options exercisable	1,825
Aggregate Intrinsic Value, Options vested and expected to vest	$ 1,997

Stock-Based Compensation - Restricted Stock Units (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Weighted Average Exercise Price Per Share
Unrecognized compensation expense, weighted-average period expected to be recognized	3 years 3 months 18 days
2016 Employee Incentive Plan \| RSU
Number of Restricted Stock Units
Granted \| shares	30,680
Balance, end of period \| shares	30,680
Weighted Average Exercise Price Per Share
Granted (price per share) \| $ / shares	$ 10.55
Balance, end of period (price per share) \| $ / shares	$ 10.55
Unrecognized stock-based compensation expense \| $	$ 260,000
Unrecognized compensation expense, weighted-average period expected to be recognized	2 years 6 months

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based compensation expense
Stock-based compensation expense	$ 2,048	$ 1,141	$ 416
Research and Development
Share-based compensation expense
Stock-based compensation expense	488	403	169
General and Administrative
Share-based compensation expense
Stock-based compensation expense	1,297	637	190
Sales and Marketing
Share-based compensation expense
Stock-based compensation expense	$ 263	$ 101	$ 57

Stock-Based Compensation - Schedule of Fair Value of Employee Stock Options (Details) - Options to Purchase Common Stock	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employees
Share-based Compensation
Expected volatility, Minimum	46.70%	42.60%	44.10%
Expected volatility, Maximum	52.00%	45.30%	48.90%
Risk-free interest rate, Minimum	1.85%	1.12%	1.51%
Risk-free interest rate, Maximum	2.14%	2.26%	1.79%
Dividend yield	0.00%	0.00%	0.00%
Employees \| Minimum
Share-based Compensation
Expected term (in years)	5 years 3 months 18 days	4 years 9 months 18 days	5 years 7 months 6 days
Employees \| Maximum
Share-based Compensation
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Non-Employee
Share-based Compensation
Expected volatility, Minimum	46.70%	52.30%	51.60%
Expected volatility, Maximum	60.50%	52.70%	52.90%
Risk-free interest rate, Minimum	2.09%	1.94%	1.72%
Risk-free interest rate, Maximum	2.44%	2.41%	2.02%
Non-Employee \| Minimum
Share-based Compensation
Expected term (in years)	7 years 2 months 12 days	9 years 6 months	6 years 7 months 6 days
Non-Employee \| Maximum
Share-based Compensation
Expected term (in years)	9 years 7 months 6 days	9 years 9 months 18 days	9 years 1 month 6 days
2016 Employee Stock Purchase Plan
Share-based Compensation
Expected volatility, Minimum	49.30%
Expected volatility, Maximum	72.70%
Risk-free interest rate, Minimum	0.49%
Risk-free interest rate, Maximum	1.02%
2016 Employee Stock Purchase Plan \| Minimum
Share-based Compensation
Expected term (in years)	6 months
2016 Employee Stock Purchase Plan \| Maximum
Share-based Compensation
Expected term (in years)	1 year

Related Party Transactions (Details)					1 Months Ended		4 Months Ended	12 Months Ended
Related Party Transactions (Details)	Oct. 07, 2016 USD ($) shares	Aug. 21, 2016 shares	Oct. 21, 2014 $ / shares shares	Oct. 17, 2014	Aug. 31, 2016 USD ($) item	Jan. 31, 2016 USD ($) item	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) item $ / shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Related Party Transactions
Loss on extinguishment of debt								$ (246,000)
Due from related party							$ 486,000	612,000	$ 486,000
Amounts due to related parties							1,359,000	1,694,000	1,359,000
Research and development expense								25,437,000	19,233,000	$ 21,126,000
Non-cash compensation expense (income)								1,472,000	965,000	$ 1,761,000
Inventory, Net							5,069,000	9,837,000	$ 5,069,000
Common Stock
Related Party Transactions
Conversion of convertible promissory notes to common stock (in shares) \| shares									1,361,009
Number of shares sold \| shares									10,639	1,558
Global Foundries \| Research and Development \| Common Stock
Related Party Transactions
Non-cash compensation expense (income)								1,500,000	$ 965,000	$ 1,800,000
Freescale
Related Party Transactions
Due from related party							486,000	587,000	486,000
Amounts due to related parties							380,000	945,000	380,000
Rent paid								1,000,000	1,100,000	1,000,000
Inventory, Net							2,500,000	3,100,000	2,500,000	3,900,000
Related party sales								2,300,000	2,400,000	3,500,000
Freescale \| Wafers
Related Party Transactions
Purchases								1,400,000	904,000
Product purchased which is included in inventory								638,000	505,000
Joint Development Agreement \| Global Foundries
Related Party Transactions
Agreement Term				4 years
Period to Repurchase Shares			1 year
Period of possession of exclusive right to manufacture after qualification of device				3 years
Period of possession of exclusive right to manufacture after completion of device development work				4 years
Due from related party							0	25,000	0
Amounts due to related parties							$ 979,000	749,000	979,000
Purchase of research and development equipment								747,000	0
Research and development expense								$ 5,200,000	2,900,000	3,600,000
Number of milestones \| item					3
First milestone payment due per the agreement					$ 569,000
Second milestone payment due per the agreement					650,000
Third milestone payment due per the agreement					406,000
Number of milestones achieved \| item								2
Milestone revenue								$ 1,600,000	$ 0	$ 0
Joint Development Agreement \| Global Foundries \| Common Stock
Related Party Transactions
Number of shares sold \| shares			461,538
Shares sold, price per share \| $ / shares			$ 0.00026
Number of shares of common stock, vested \| shares		211,538					153,846
Number of shares of common stock, unvested \| shares							96,153		96,153
Estimated fair value of common stock per share \| $ / shares							$ 8.29	$ 7.50	$ 8.29	$ 13.52
Joint Development Agreement \| Global Foundries \| Series B Redeemable Convertible Preferred Stock
Related Party Transactions
Number of shares sold \| shares			192,307
Shares sold, price per share \| $ / shares			$ 26.00
2016 Convertible Promissory Notes \| Stockholders
Related Party Transactions
Debt instrument, aggregate amount						$ 5,000,000
Debt instrument, interest rate						5.00%
Debt instrument, convertible, equity issuance trigger						$ 5,000,000
Debt instrument, threshold percentage						80.00%
Multiple factor for cash payment \| item						3
Debt instrument, carrying value	$ 5,200,000
Unamortized discount	74,000
Derivative liability	70,000
Loss on extinguishment of debt	0
2016 Convertible Promissory Notes \| Stockholders \| Common Stock
Related Party Transactions
Accrued interest	$ 176,000
Conversion of convertible promissory notes to common stock (in shares) \| shares	808,747
2016 Bridge Notes \| Stockholders
Related Party Transactions
Debt instrument, aggregate amount					$ 3,500,000
Debt instrument, interest rate					5.00%
Debt instrument, convertible, equity issuance trigger					$ 5,000,000
Debt instrument, threshold percentage					80.00%
Multiple factor for cash payment \| item					3
Debt instrument, carrying value	$ 3,500,000
Unamortized discount	122,000				$ 264,000	$ 653,000
Derivative liability	50,000
Loss on extinguishment of debt	0
2016 Bridge Notes \| Stockholders \| Common Stock
Related Party Transactions
Accrued interest	$ 35,000
Conversion of convertible promissory notes to common stock (in shares) \| shares	552,262

Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Geographic Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Geographic Information
Total revenue	$ 10,123	$ 9,008	$ 8,925	$ 7,880	$ 7,064	$ 7,164	$ 6,659	$ 6,207	$ 35,936	$ 27,094	$ 26,546
United States
Geographic Information
Total revenue									4,759	4,321	5,362
Singapore
Geographic Information
Total revenue									8,067	5,467	4,614
Japan
Geographic Information
Total revenue									4,128	3,285	2,280
Germany
Geographic Information
Total revenue									2,964	3,013	3,546
Taiwan
Geographic Information
Total revenue									2,076	2,161	3,759
Hong Kong
Geographic Information
Total revenue									2,179	2,122	2,744
All other
Geographic Information
Total revenue									$ 11,763	$ 6,725	$ 4,241

Income Taxes - Reconciliation Effective Tax Rate (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Provision for income taxes		$ 0	$ 0	$ 0
Reconciliation of statutory federal income tax
Tax at statutory federal rate	(35.00%)	(34.00%)	(34.00%)	(34.00%)
State taxes, net of federal benefit		(1.40%)	(1.50%)	(1.90%)
Stock-based compensation		(0.80%)	1.30%	0.80%
Nondeductible fair value adjustment			(2.50%)
Nondeductible interest			2.00%
Change in valuation allowance		(34.20%)	33.30%	34.30%
Federal tax rate change		70.20%
Other		0.20%	1.40%	0.80%
Provision for income taxes		0.00%	0.00%	0.00%

Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 22,586	$ 29,469
Inventory	1,520	1,187
Accruals	401	902
Depreciation and amortization	60	105
Other	1,228	1,312
Gross deferred tax assets	25,795	32,975
Valuation allowance	(25,721)	(32,850)
Deferred tax assets	74	125
Deferred tax liabilities:
Prepaid expenses	(74)	(125)
Deferred tax liabilities	(74)	(125)
Increase in valuation allowance	$ (7,100)	$ 5,300

Income Taxes - Net operating loss carryforwards and Tax Act (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net operating loss carryforwards
Tax at statutory federal rate	35.00%		34.00%	34.00%	34.00%
Decrease in deferred tax assets	$ 14.8		$ 14.8
Net effect of the tax reform enactment	0.0		0.0
Forecast
Net operating loss carryforwards
Tax at statutory federal rate		21.00%
Federal
Net operating loss carryforwards
Net operating loss carryforwards	100.1		100.1
State
Net operating loss carryforwards
Net operating loss carryforwards	$ 39.3		$ 39.3

Net Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss	$ (4,381)	$ (5,446)	$ (5,187)	$ (6,086)	$ (5,308)	$ (1,444)	$ (5,416)	$ (4,540)	$ (21,100)	$ (16,708)	$ (18,183)
Denominator:
Weighted-average common shares outstanding									12,640,094	5,117,226	3,013,743
Less: weighted-average unvested common shares subjected to repurchase									(155,110)	(378,730)	(461,538)
Weighted-average common shares outstanding used to calculate net loss per common share, basic and diluted									12,484,984	4,738,496	2,552,205
Net loss per common share, basic and diluted	$ (0.35)	$ (0.43)	$ (0.42)	$ (0.49)	$ (0.48)	$ (0.54)	$ (2.12)	$ (1.78)	$ (1.69)	$ (3.53)	$ (7.12)

Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Diluted Net Loss Per Common Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	1,747,718	1,653,958	3,902,602
Redeemable Convertible Preferred Stock
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share			2,486,199
Options to Purchase Common Stock
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	1,593,195	1,414,730	927,175
RSU
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	30,680
Common Stock Subject to Repurchase
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	96,153	211,538	461,538
Redeemable Convertible Preferred Stock Warrants
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share			27,690
Common Stock Warrants
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	27,690	27,690

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data (Unaudited)
Total revenue	$ 10,123	$ 9,008	$ 8,925	$ 7,880	$ 7,064	$ 7,164	$ 6,659	$ 6,207	$ 35,936	$ 27,094	$ 26,546
Gross profit	6,221	5,255	5,792	4,217	3,232	4,305	3,500	3,662	21,485	14,699	13,978
Net loss	$ (4,381)	$ (5,446)	$ (5,187)	$ (6,086)	$ (5,308)	$ (1,444)	$ (5,416)	$ (4,540)	$ (21,100)	$ (16,708)	$ (18,183)
Net loss per common share, basic and diluted	$ (0.35)	$ (0.43)	$ (0.42)	$ (0.49)	$ (0.48)	$ (0.54)	$ (2.12)	$ (1.78)	$ (1.69)	$ (3.53)	$ (7.12)

Subsequent Events - (Details) - USD ($)	1 Months Ended
Subsequent Events - (Details) - USD ($)	Feb. 28, 2018	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent events
Exercise price (in dollars per share)			$ 8.88	$ 5.28	$ 4.43
Follow-on offering
Subsequent events
Proceeds, net of underwriting discounts and commissions, but before offering costs	$ 24,800,000
Subsequent Events \| Follow-on offering
Subsequent events
Number of shares sold	3,772,447
Offering price	$ 7.00
Proceeds, net of underwriting discounts and commissions, but before offering costs	$ 24,800,000
Subsequent Events \| Chief Executive Officer
Subsequent events
Number of unvested stock option award modified	400,000
Exercise price (in dollars per share)	$ 7.64	$ 16.25
Incremental modification value	$ 600,000
Immediate vesting \| Subsequent Events \| Chief Executive Officer
Subsequent events
Incremental modification value	63,000
Remaining vesting \| Subsequent Events \| Chief Executive Officer
Subsequent events
Incremental modification value	$ 537,000

401 (k) Plan	12 Months Ended
401 (k) Plan	Dec. 31, 2017
401 (k) Plan
401 (k) Plan	8. 401(k) Plan The Company has a defined contribution employee benefit plan pursuant to Section 401(k) of the Internal Revenue Code. The plan allows eligible employees to defer a portion of their annual compensation up to certain statutory limits. At the election of the Board of Directors, the Company may elect to match employee contributions but has not done so to date.