Employee Benefits and Stock-based Compensation (Tables)

12 Months Ended

Jan. 31, 2013

Classification of Stock-Based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Year Ended January 31,
	2013		2012		2011
	(in thousands)
Stock-based compensation:
Cost of revenue	$	92	$	52	$	41
Research and development		2,942		1,821		1,058
Selling, general and administrative		1,965		1,743		757
Total stock-based compensation	$	4,999	$	3,616	$	1,856

Weighted-Average Assumptions Used to Estimate Fair Value

The following table sets forth the weighted-average assumptions used to estimate the fair value of the stock options and employee stock purchase plan awards for the periods indicated:

	Year Ended January 31,
	2013			2012			2011
Stock Options:
Volatility		66	%		65	%		63	%
Risk-free interest rate		0.91	%		1.64	%		1.79	%
Expected term (years)		6.05			6.05			6.05
Dividend yield		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		51	%		N/A			N/A
Risk-free interest rate		0.18	%		N/A			N/A
Expected term (years)		0.94			N/A			N/A
Dividend yield		0	%		N/A			N/A

Stock Option Activities

The following table summarizes stock option activities for the periods indicated:

	Option Outstanding
	Shares			Weighted- Average Exercise Price		Weighted- Average Grant-date Fair Value		Total Intrinsic Value of options Exercised (in thousands)		Weighted- Average Remaining Contactual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at January 31, 2010		2,952,083		$	2.73
Granted		1,024,629			8.77	$	5.12
Exercised		(100,779	)		2.11			$	670
Forfeited		(61,151	)		4.04
Outstanding at January 31, 2011		3,814,782			4.35
Granted		1,207,564			8.82	$	5.24
Exercised		(454,053	)		2.91			$	2,682
Forfeited		(192,387	)		6.78
Outstanding at January 31, 2012		4,375,906			5.63
Granted		451,071			8.79	$	5.23
Exercised		(313,827	)		3.21			$	2,087
Forfeited		(168,615	)		7.22
Outstanding at January 31, 2013		4,344,535		$	6.07						6.81	$	16,918
Exercisable at January 31, 2013		3,100,758		$	5.20						6.17	$	14,774
Vested and expected to vest at January 31, 2013		4,257,819		$	6.02						6.78	$	16,768

Restricted Stock Units Activities

The following table summarizes restricted stock units activities for the year ended January 31, 2013:

	Shares			Weighted- Average Grant-Date Fair Value
Unvested at January 31, 2012		—		$	—
Granted		345,171			9.99
Vested		—			—
Forfeited		(5,954	)		9.99
Unvested at January, 2013		339,217		$	9.99