A temperature compensated relaxation oscillator for SoC implementations

A temperature and supply independent on-chip reference relaxation oscillator for low voltage design is described. The frequency of oscillation is mainly a function of a PVT robust biasing current. The comparator for the relaxation oscillator is replaced with a high speed common-source stage to eliminate the temperature dependency of the comparator delay. The current sources and voltages are biased by a PVT robust references derived from a bandgap circuitry. This oscillator is designed in TSMC 65 nm CMOS process to operate with a minimum supply voltage of 1.4 V and consumes 100 μW at 157 MHz frequency of oscillation. The oscillator exhibits frequency variation of 1.6% for supply changes from 1.4 V to 1.9 V, and ±1.2% for temperature changes from 20°C to 120°C.