Monolithic implementation of phase shifted switched capacitor step-down DC-DC converter for portable power applications

This paper presents analysis and design of a reconfigurable switched capacitor (SC) step-down DC-DC converter architecture suitable for on-chip integrated portable power supplies. Comprising basic SC cells, the proposed DC-DC converter is modular in architecture, and can be viewed as a dual of the multiphase buck converter architecture. The SC converter with integrated capacitors is designed in a standard 180 nm CMOS process to operate in 1/3 and 1/2 conversion ratio modes. The converter is designed to operate with input voltage varying from 2.7V to 5.5V, and switching frequency varying from 10 MHz to 70 MHz, while delivering up to 250mA load current at 1.3V output voltage. SPICE simulation results based on detailed process models are presented. It is shown that efficiency is significantly higher than in a linear regulator operating over the complete specified input voltage range, and also reduces the off-chip input and output filter capacitor requirement.