A 90-nm CMOS high efficiency on chip DC-DC converter for ultra-low power low cost applications

It is widely recognized that adaptive control of the power supply is one of the most effective variables to achieve energy-efficient computation. Most on-chip dc-dc conversion systems have relied on buck converters with off-chip LC filters. In this paper, we describe the development of fully integrated on-chip dc-dc down conversion system that combines switched-capacitor voltage divider and linear regulator. The converter was designed with 90-nm standard CMOS process. No external components are required. With an input voltage of 2.6V, the converter achieves step-down voltage conversion with an output voltage equal to 1.1V and a maximum efficiency of 63%. The converter employs a dynamic control loop to automatically adjust the switching frequency with the load current variation. Its switching frequency varies from 2MHz to 38MHz while load current is between 1mA and 16mA respectively. The use of switched-capacitor supply offers better efficiency than what is achievable with linear regulator alone.