Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (17,754)	$ (21,100)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,450	1,191
Loss on disposal of property and equipment	19
Stock-based compensation	2,668	2,048
Non-cash loss on extinguishment of debt		185
Non-cash interest expense	375	297
Compensation expense related to vesting of common stock to GLOBALFOUNDRIES	753	1,472
Changes in operating assets and liabilities:
Accounts receivable	(3,816)	(385)
Inventory	694	(3,871)
Prepaid expenses and other current assets	(98)	460
Other assets		(23)
Accounts payable	(178)	809
Accrued liabilities	1,253	136
Deferred income on shipments to distributors		(107)
Shipping term reversal	(39)
Net cash used in operating activities	(14,673)	(18,888)
Cash flows from investing activities
Purchases of property and equipment	(1,914)	(3,070)
Net cash used in investing activities	(1,914)	(3,070)
Cash flows from financing activities
Proceeds from the issuance of common stock, net of offering costs	24,524
Proceeds from debt	1,000	12,000
Payments on debt	(1,000)	(8,356)
Payments of debt issuance costs		(49)
Payments on capital lease obligation	(11)	(7)
Proceeds from exercise of stock options and purchase of shares in employee stock purchase plan	2,503	1,593
Net cash provided by financing activities	27,016	5,181
Net increase (decrease) in cash and cash equivalents	10,429	(16,777)
Cash and cash equivalents at beginning of period	12,950	29,727
Cash and cash equivalents at end of period	23,379	12,950
Supplementary cash flow information:
Interest paid	504	467
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payable	11	116
Purchases of property and equipment under capital lease obligations		$ 31
Issuance of warrant in lieu of financing costs	$ 43