This excerpt taken from the SLAB 10-K filed Feb 7, 2007.
Stock-based compensation costs are generally based on the fair value calculated from the Black-Scholes option-pricing model on the date of grant for stock options and on the date of enrollment for the Purchase Plan. RSU fair values generally equal their intrinsic value on the date of grant.
The fair values of stock grants are amortized as compensation expense on a straight-line basis over the vesting period of the grants. Compensation expense recognized is shown in the operating activities section of the consolidated statements of cash flow.
Silicon Laboratories Inc.