A 150nW 32 kHz mobility-compensated relaxation oscillator with +/−30ppm/°C temperature stability

Abstract

A relaxation oscillator is presented that makes use of a current-mode Schmitt trigger to reduce the effects of process, voltage and temperature (PVT) variations. A detailed analysis of the oscillator, including the temperature performance, is presented and verified by experimental results. A test chip with a typical frequency of 32 kHz was fabricated in a 0.18 μm standard CMOS process. The measured frequency variations were +/- 30 ppm/°C for temperature variation from -20 °C to 80°C and +/- 500 ppm/V for supply voltage variation from 0.7 V to 1.8 V. The short term stability is 66 ppm (2 ns) of jitter while the long term stability is 500 ppm of Allan deviation after 10 seconds. A careful design results in a total area of 0.1 mm2 and a power consumption of 150 nW.