Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016	Oct. 01, 2017	Sep. 25, 2016
Income Statement [Abstract]
Revenue	$ 50,108	$ 34,105	$ 135,084	$ 91,577
Cost of revenue	25,591	17,247	68,212	46,452
Gross profit	24,517	16,858	66,872	45,125
Operating expenses:
Research and development	15,011	11,162	43,699	32,913
Sales and marketing	3,363	2,172	9,553	5,571
General and administrative	3,735	3,248	11,231	7,802
Total operating expenses	22,109	16,582	64,483	46,286
Income (loss) from operations	2,408	276	2,389	(1,161)
Interest expense	(103)	(189)	(442)	(414)
Other income (expense), net	223	(52)	610	(300)
Income (loss) before income taxes	2,528	35	2,557	(1,875)
Benefit (provision) for income taxes	274	(14)	(470)	(52)
Net income (loss)	$ 2,802	$ 21	$ 2,087	$ (1,927)
Net income (loss) per share:
Basic (usd per share)	$ 0.08	$ 0.02	$ 0.06	$ (1.84)
Diluted (usd per share)	$ 0.07	$ 0.00	$ 0.05	$ (1.84)
Weighted average shares used to compute basic and diluted net income (loss) per share:
Basic (in shares)	34,734	1,157	33,907	1,048
Diluted (in shares)	38,525	29,974	38,419	1,048