Analog Circuit Design Volume Three

Chapter 191

Replace ORing diodes with MOSFETs to reduce heat and save space

James Herr and Mitchell Lee

Abstract

The LTC4354, negative voltage diode-OR controller that realizes near-ideal diode behavior, is described.

Keywords

ORing diode

LTC4354

Introduction

High availability telecom systems employ redundant power supplies or battery feeds to enhance system reliability. Discrete diodes are commonly used to combine these power sources at the point of load. The disadvantage of this approach is the significant forward voltage drop and resulting power dissipation, even with Schottky diodes. This drop also reduces the available supply voltage, which is sometimes critical at the low end of the input operating range. A circuit with “ideal” ...