A 32.55-kHz, 472-nW, 120ppm/°C, fully on-chip, variation tolerant CMOS relaxation oscillator for a real-time clock application

Abstract

This paper proposes an ultra-low power fully on-chip CMOS relaxation oscillator (ROSC) for a real-time clock application. The circuit has a distinctive feature in compensation architecture of a comparator's non-idealities caused by offset voltage and delay time. The ROSC can generate a stable and higher oscillation clock frequency without increasing power by using a low reference voltage and employing a novel compensation architecture for comparators. Measurement results in a 0.18-μm CMOS process demonstrated that the circuit can generate a stable clock frequency of 32.55 kHz. The power dissipation was 472 nW. Measured line regulation and temperature coefficient were 1.1%/V and 120ppm/°C, respectively.