A 12.4-kHz on-chip RC oscillator with comparator offset cancellation for PVT variation tolerance

This paper presents a low-power on-chip RC oscillator with compensation for temperature and supply voltage variation. This circuit is based on a conventional on-chip oscillator, with only a capacitor and a comparator to avoid mismatch. Multiple current sources flow through the same resistor to generate a reference voltage. This is complemented with the dynamic element matching technique to reduce the inherent mismatch between current sources. A comparator offset compensation scheme is also proposed in this circuit. Simulation results show that the circuit can generate a stable frequency of 12.4 kHz. The power consumption is 9.3 μW. The temperature coefficient is ±0.12% across -40°C to 120°C and the supply voltage variation coefficient is ±0.08% ranging from 1 V to 2 V.