A 0.16mm2 completely on-chip switched-capacitor DC-DC converter using digital capacitance modulation for LDO replacement in 45nm CMOS

Reducing power consumption through VDD scaling is a major trend in nanometer CMOS circuits. In modern wireless SoCs, multiple power domains operate below 1.2V and draw less than 10mA of current. Currently, these domains are powered from a 1.8V rail through a low drop-out linear regulator (LDO). The 1.8V rail is obtained from a Li-ion battery using a switching regulator with off-chip passives. It is highly inefficient to power circuit blocks that operate below 1.2V through LDOs. Switched-capacitor (SC) DC-DC converters are a viable solution to replace LDOs in some on-chip power domains but they currently occupy a large on-chip area [1]. Also, the voltage regulation schemes employed by current SC converters are either unsuitable in wireless systems or do not provide high efficiencies in on-chip use cases due to the dominance of bottom-plate and switching losses [2]. In this paper, a completely on-chip SC DC-DC converter that uses a digital capacitance modulation scheme to achieve voltage regulation is presented. The converter occupies only 0.16mm2 in total area and provides up to 8mA of current to output voltages between 0.8V to 1V from a 1.8V input while switching at 30MHz.