Condensed Statement of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss	$ (8,646)	$ (11,273)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	729	510
Loss on disposal of property and equipment	19
Stock-based compensation	1,342	839
Non-cash loss on extinguishment of debt		185
Non-cash interest expense	200	119
Compensation expense related to vesting of common stock to GLOBALFOUNDRIES	462	716
Changes in operating assets and liabilities:
Accounts receivable	(1,391)	(524)
Inventory	940	(1,584)
Prepaid expenses and other current assets	(635)	48
Other assets	(136)	(11)
Accounts payable	51	(158)
Accrued liabilities	2,591	80
Deferred income on shipments to distributors		(237)
Shipping term reversal	(39)
Net cash used in operating activities	(4,513)	(11,290)
Cash flows from investing activities
Purchases of property and equipment	(347)	(1,704)
Net cash used in investing activities	(347)	(1,704)
Cash flows from financing activities
Proceeds from issuance of common stock, net of offering costs	24,609
Proceeds from debt		12,000
Payments on debt	(1,000)	(8,356)
Payments of debt issuance costs		(49)
Payments on capital lease obligation	(6)	(7)
Proceeds from exercise of stock options and purchase of shares in employee stock purchase plan	1,032	855
Net cash provided by financing activities	24,635	4,443
Net increase (decrease) in cash and cash equivalents	19,775	(8,551)
Cash and cash equivalents at beginning of period	12,950	29,727
Cash and cash equivalents at end of period	32,725	21,176
Supplementary cash flow information:
Interest paid	233	288
Non-cash investing and financing activities:
Purchase of property and equipment in accounts payable	$ 27	$ 560