Programmable digital controller for multi-output DC-DC converters with a time-shared inductor

Abstract

This paper introduces a low power digital PFM controller for multi-output dc-dc converters suitable for integration in modern low-power management systems. It utilizes only one inductor to provide multiple output voltages and has very low power consumption. In addition, its reference voltages and switching frequency can be programmed dynamically. To achieve these characteristics two new key functional blocks are developed, namely Σ-Δ programmable delay-line based comparator utilizing natural filtering of delay cells and on-time control logic. The controller is implemented both on FPGA and a 0.18-μm CMOS application specific IC. Experimental results obtained with a 1 W, 9 V, four-output buck prototype and IC simulations successfully verify controller operation.