Temperature and process independent ring-oscillator using compact compensation technic

The parameters of CMOS device will be affected by the variation of temperature and process variation. Due to these variations, a ring oscillator implemented in CMOS process will not have an constant output frequency which is designed in CAD tools. In order to get a constant frequency, additional circuit is needed to compensate the variation in both temperature and process. After investigate the drawback of the state of art design, a modified structure is proposed, which don't need to use an op-amp to boost the compensation bias voltage up. Because no need of the boosting op-amp, the compensation circuit will get benefits to offset voltage, power consumption, loading effect and chip area, etc. According to the Cadence simulation result based on TSMC 0.18μm RF CMOS process, less than 2% frequency variation is obtained from -40 to 125°C in three different process corners (SS/TT/FF). The total core power consumption is less than 220uW, except the external LDO.