Integrated relaxation oscillator with no comparator for energy harvesting

Abstract

A fully-integrated 12 kHz relaxation oscillator for energy harvesting application is presented. The oscillator has no comparator and no reference voltage. A conventional comparator has been replaced by a pseudo-inverter chain to avoid comparator offset effect. Moreover, inverter threshold variation has no impact on the frequency. The circuit has been designed with 0.18 µm standard CMOS process. The oscillator operates in subthreshold region and consumes an ultra-low power of 120 nW. A temperature coefficient of 31 ppm/°C has been achieved over −40 to 90°C.

On‐chip dual‐phase charge‐transfer relaxation oscillator with comparator offset cancellation

“…On-chip relaxation oscillator is an attractive structure for low power operation with high accuracy [1]. The relaxation oscillators are generally adopted the structures of current mode [2], exponential RC time-constant mode [3], or voltage mode [4,5]. The frequency stability generally suffers from process, voltage, and temperature (PVT) variation.…”