A Low-Power Comparator-Less Relaxation Oscillator

This paper proposes an integrated low-power relaxation oscillator using a feedback voltage to boost the swing of the capacitor. A conventional comparator is replaced by an inverter chain, and the static power consumption could be greatly reduced. Moreover, the variation on the threshold of the inverter has no affection on the frequency stability. Since the feedback voltage is proportional to the power supply, the capacitor charging and discharging current which is proportional to the power supply is designed to avoid the frequency variation influenced by the supply voltage. The circuit has been designed with 0.18 mu m CMOS process. The frequency of the oscillator is designed to 190 kHz. The simulation shows that the worst supply sensitivity of the oscillator achieves 0.84%/V, the average temperature coefficient of the oscillation frequency is 197 ppm/degrees C, and the power consumption is 2.4 mu W.