A 32-ppm/°C 0.9-nW/kHz Relaxation Oscillator with Event-Driven Architecture and Charge Reuse Technique

This paper presents a dual-phase RC-based relaxation oscillator (RxO) with low temperature coefficient (TC) and high power efficiency achieved simultaneously for energy-constrained Internet-of-Things (IoT) applications with burst-mode requirements. Its circuit-level event-driven architecture reduces the duty cycle of power-hungry blocks, saving power while posing little performance penalty. In addition, the charge reuse technique further reduces the power consumption for the always-on detecting circuit. Implemented in a 0.18-μm CMOS process, the 180-kHz relaxation oscillator exhibits a frequency deviation of ± 0.26% against temperature (-40 to 125 ° C) from Monte-Carlo simulation (N=30), leading to a low temperature coefficient of 32 ppm/° C. The simulated power consumption is 163 nW, resulting in power efficiency of 0.9 nW/kHz.