A Single-inductor Dual-output Step-down Dc - Dc Converter Design

With continuous shrinking of consumer products especially portable equipment it is necessary to realize high density system routing and placement on PCB. Minimizing the off-chip components is becoming one of the targets when doing chip design. High efficiency DC-DC conversion plays an important role in extending battery life. Bulky inductors occupy a large volume of the system and it is difficult to be integrated so realizing dual or multiple outputs only using one inductor is very attractive.Study and design of a single inductor dual output buck DC-DC converter is introduced in this dissertation. Method of state-space averaging and some basic principle are first introduced based on single output DC-DC converter. Model of dual output converter is established according to the comparison to the single output structure. An optimized control method is used to achieve better performance such as die size and output voltage ripple. A prototype circuit is designed using TSMC 2.5V/5V 0.25μm CMOS process and some circuit block improvements have been made such as current sensing unit. The chip is experimental verified and our design is proved to be feasible.