Design of a Ring Oscillator with Temperature and Process Compensation Adopting a Novel Method

Due to the variation of temperature and process corner, a ring oscillator implemented in a CMOS process will not have a constant output frequency. In order to get a relatively constant frequency, an additional circuit is needed to compensate the variation in both temperature and process corner. Based on the traditional method of ring-oscillation linear compensation, a new type of compensation coefficient least-squares algorithm is presented in this paper. This method is used to approximate the optimal solution of the system of equations, and the best possible compensation control voltage group is obtained. The proposed oscillator has a center frequency of 9.844 MHz in the temperature range of -20 degrees C to 80 degrees C and at various process corners, with a maximum deviation of only 1.5% (pre-simulation) and 1.7% (post-simulation). The design was simulated and verified in SMIC 0.18-mu m CMOS technology, uses a 2.5-V supply, and consumes a maximum power of 1mW.