A Hysteretic Buck Converter with 92.1% Maximum Efficiency Designed for Ultra-Low Power and Fast Wake-Up SoC Applications

This paper presents a dc-dc converter for integration in the power management unit of an ultra-low power microcontroller. The converter is designed to significantly reduce the wake-up energy and startup delay of the supplied core. The use of a minimized output capacitor is the key factor to save the wake-up energy. The converter is buffered with only 56 nF and guarantees a stable output of 1.2 V with a voltage ripple smaller than 30 mV. The controller of the proposed dc-dc converter is based on a predictive peak current control that allows the system to control the energy transfer at extremely low power consumption. The proposed circuit is implemented in 130-nm CMOS technology with an area of only 0.14 mm². It achieves a high conversion efficiency of 92.1% and a small quiescent current of 440 nA. It operates from 1.8 to 3.3 V with a maximum load of 2.65 mA.