Balance Sheet Components (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017
Inventories:
Work-in-process	$ 2,852	$ 2,894
Finished goods	698	665
Inventories	3,550	3,559
Other current assets:
Prepaid expenses	1,196	836
Other	230	161
Other current assets	1,426	997
Property and equipment:
Property and equipment, gross	14,586	14,855
Accumulated depreciation and amortization	(12,469)	(12,480)
Property and equipment, net	2,117	2,375
Accrued liabilities:
Employee related accruals	1,431	1,143
Other	551	510
Accrued liabilities	1,982	1,653
Equipment
Property and equipment:
Property and equipment, gross	11,058	10,996
Software
Property and equipment:
Property and equipment, gross	2,811	3,139
Furniture and fixtures
Property and equipment:
Property and equipment, gross	42	46
Leasehold improvements
Property and equipment:
Property and equipment, gross	$ 675	$ 674