A successive approximation based process-invariant ring oscillator

In this paper, we present a successive approximation based compensation scheme to minimize the process and temperature induced variation in a ring oscillator topology. This scheme is able to reduce the standard deviation of the oscillation frequency to less than 2%, as compared to more than 9.3% in a typical uncompensated ring oscillator implemented in 65 nm CMOS process. The improved variation performance of the proposed scheme is supported by simulation results over a wide frequency range and under different process and temperature conditions in 65 nm technology.