A low power relaxation oscillator with process insensitive auto-calibration scheme

In this paper, we present an auto-calibrated process insensitive relaxation oscillator. A process sensitivity of 1.36% is achieved by automatically sensing the output clock frequency spread and alternatively adjusting the capacitor-used for charging and discharging. In addition, a time to digital converter is adopted for tuning the compensating capacitor. Moreover, the proposed oscillator with on-chip calibration scheme, implemented by UMC 0.18μm 1P6M standard process, is validated by our reported extensive post-layout simulation results. A frequency of 32.7 kHz can be generated by operating the system under 1V supply voltage.