p. em. Includes bibliographical references and index.

p. em. Includes bibliographical references and index.

Abstract-This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm 2 of silicon area in a standard 0.5 digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.Index Terms-DC-DC switch-mode power conversion, digital control, digital pulse width modulation.

Abstract-In dc-to-dc conversion applications that require a large range of input andlor output voltages, conventional PWM converter topologies must operate at extremely low duty ratios, which limits the operation to lower switching frequencies because of the minimum ONtime of the transistor switch. This is eliminated in a new class of singletransistor PWM converters featuring voltage conversion ratios with quadratic dependence on duty ratio. Practical circuit examples operating at 0.5 MHz are described.

Theoretical performance limits of twophase switched-capacitor (SC) dc-dc converters are discussed in this paper. For a given number of capacitors k, the complete set of attainable dc conversion ratios is found. The maximum step-up or stepdown ratio is given by the kth Fibonacci number, while the bound on the number of switches required in any SC circuit is 3k -2. Practical implications, illustrated by several SC converter examples, include savings in the number of components required for a given application, and the ability to construct SC converters that can maintain the output voltage regulation and high conversion efficiency over a wide range of input voltage variations. Limits found for the output resistance and efflciency can be used for selection and comparison of S C converters.