A fully-integrated VCO-based analog-assisted-digital low-dropout regulator with feed-forward PSR enhancement for energy-harvesting wireless sensor node

Abstract

The sensor nodes within wireless sensor networks (WSNs) can harvest energy from the environment to supplement their power needs. The sensor node requires a low-voltage regulator to condition the weak and unstable harvested energy. This paper presents a self-clocked fully-integrated feedforward-biased hybrid low-dropout regulator (FFB-HLDO) with a dual differential VCO (DD-VCO) pair for WSN sensor applications. The proposed HLDO is fully integrated without load capacitor. To enhance the Power Supply Rejection (PSR) performance, an analog feedforward biased (AFFB) technique is proposed to reduce supply ripples. Besides, a distortion module (DM) is proposed to improve the transient response. Implemented in a 65 nm CMOS technology, this capacitor-less and self-clocked HLDO can provide the minimum output of 0.3V and the maximum output of 1.5V from 0.55–1.6V input, and the area is 0.0123 mm². For the maximum load current of 0.26 mA, the peak current efficiency is 98.9%. With a quiescent current of 300 nA, the frequency of 0-dB-PSR is 100 MHz.