Stock-Based Compensation (Tables)

3 Months Ended

Mar. 28, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense (in thousands):

	Three months ended
	March 28, 2014		March 29, 2013
Stock-based compensation in:
Cost of revenue	$	516	$	611
Research and development expense	1,101		1,203
Selling, general and administrative expense	2,190		2,085
Total stock-based compensation in operating expense	3,291		3,288
Total stock-based compensation	$	3,807	$	3,899

Valuation Assumptions for Stock Options

The Company estimated the fair value of all employee stock options using a Black-Scholes valuation model with the following weighted average assumptions:

	Three months ended
	March 28, 2014		March 29, 2013
Expected term (years)	4.70		4.70
Volatility	40	%	52	%
Risk-free interest rate	1.7	%	0.8	%
Expected dividends	0.0	%	0.0	%

Employee Stock Purchase Plan

The call option and put option were valued using the Black-Scholes option pricing model. The weighted average fair value of the Company's ESPP shares at purchase dates was estimated using the following weighted average assumptions during the three months endedMarch 28, 2014 and March 29, 2013:

	Purchase Period Ending
	June 30, 2014		June 30, 2013
Expected term (years)	0.50		0.49
Volatility	29	%	32	%
Risk-free interest rate	0.1	%	0.2	%
Expected dividends	0.0	%	0.0	%
Estimated weighted average fair value per share at purchase date	$1.71		$1.20