Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity

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Stockholders' Equity
3 Months Ended
Mar. 31, 2013
Stockholders' Equity Note [Abstract]  
Stockholders' Equity
Stockholders’ Equity
In 2002, we adopted the 2002 Stock Plan (the “2002 Plan”), pursuant to which our board of directors issued incentive stock options, non-statutory stock options (options that do not qualify as incentive stock options) and restricted stock to our employees, officers, directors or consultants. In March 2010, our board of directors and stockholders approved the 2010 Equity Incentive Award Plan (the “2010 Plan”), which became effective upon the completion of our IPO in April 2010. A total of 1,100,000 shares of common stock were initially reserved for future issuance under the 2010 Plan and any shares of common stock reserved for future grant or issuance under our 2002 Plan that remained unissued at the time of completion of the IPO became available for future grant or issuance under the 2010 Plan. In addition, the shares reserved for issuance pursuant to the exercise of any outstanding awards under the 2002 Plan that expire unexercised will also become available for future issuance under the 2010 Plan. The 2010 Plan also provides for automatic annual increases in the number of shares reserved for future issuance, and during the three months ended March 31, 2013 an additional 1,506,707 shares were reserved under the 2010 plan as a result of this provision. As of March 31, 2013, we had a total of 12,029,742 shares of common stock reserved for issuance under our 2010 Plan and no shares available for issuance under the 2002 Plan.
We awarded 833,698 restricted stock units (“RSU”) under the 2010 Plan during the three months ended March 31, 2013. The fair value of the RSU awards was calculated based on the NASDAQ quoted stock price on the date of the grant with the expense recognized over the vesting period.
During the three months ended March 31, 2013, we issued 244,379 common shares for stock options exercised and 90,428 common shares for RSUs that vested during the quarter.
Performance Stock Units
We awarded 523,048 performance stock units ("PSU") under the 2010 Plan during the three months ended March 31, 2013. The number of shares of Company common stock to be issued for each vested PSU will range between zero and two, depending on the level of performance as compared to the criteria set by our board with respect to the Company's annual cash burn for the year ended December 31, 2013. We currently estimate 100% of the performance goal will be achieved which will result in one common share issued for each vested PSU. The PSU awards vest in equal installments on March 5, 2014 and March 5, 2015. The fair value of the PSU awards was calculated based on the NASDAQ quoted stock price on the date of the grant with the expense recognized over the vesting period. For the three months ended March 31, 2013 we recorded $171,000 of stock based compensation expense related to the PSU awards.
Stockholder Rights Plan
In August 2012, our board of directors adopted a stockholder rights plan and declared a dividend of one preferred share purchase right for each share of our common stock held by stockholders of record as of September 18, 2012. Each right entitles stockholders, after the rights become exercisable, to purchase one one-thousandth of a share of our Series A Junior Participating Preferred Stock, par value $0.0001, at a purchase price of $11.35 per one thousandth of a share of Series A Junior Participating Preferred Stock. In general, the rights become exercisable when a person or group acquires 15% or more of our common stock or a tender offer for 15% or more of our common stock is announced or commenced. The rights may discourage a third-party from making an unsolicited proposal to acquire us as exercise of the rights would cause substantial dilution to a person or group that attempts to acquire us on terms not approved by our board of directors. The rights should not interfere with any merger or other business combination approved by our board of directors since the rights may be redeemed by us at $0.0001 per right at any time before any person or group acquire 15% or more of our outstanding common stock. These rights expire in September 2013.
Stock-Based Compensation Expense
We estimate the fair value of stock-based awards granted to employees and directors using the Black-Scholes option-pricing model. The Black-Scholes option-pricing model requires the use of highly subjective and complex assumptions to determine the fair value of stock-based awards, including the expected life of the option and expected volatility of the underlying stock over the expected life of the related grants. Since we were not a publicly traded entity prior to April 2010, sufficient company-specific historical volatility data was not available for reporting periods prior to the second quarter of 2012. As a result, for those periods, we estimated the expected volatility based on the historical volatility of a group of unrelated public companies within our industry. Effective for the second quarter of 2012, we determined we had sufficient company-specific historical volatility data. As a result, we estimate the expected volatility based on historical volatility of our common stock.
Due to our limited history of grant activity, the expected life of options granted to employees is calculated using the “simplified method” permitted by the SEC as the average of the total contractual term of the option and its vesting period. The risk-free rate assumption was based on United States Treasury instruments whose terms were consistent with the terms of our stock options. The expected dividend assumption was based on our history and expectation of dividend payouts.
The following table presents total stock-based compensation expense included in the condensed consolidated statements of operations (in thousands):
 
Three Months Ended March 31,
 
2013
 
2012
Research and development
$
527

 
$
653

Sales, general and administrative
945

 
516

 
$
1,472

 
$
1,169