This application note discusses 5V to 3.3V converters for high-performance microprocessor systems. These converters employ special techniques to ensure proper operation of the microprocessor and good heat dissipation within the computer system. The document provides a collection of 3.3V regulator circuits optimized for a 5V input and surface mount technology, categorized into linear and switching types based on current capability. Most of the circuits can be surface mounted, except for high current linear regulators that may require different components.
This document describes techniques for generating a 3.3V supply from a 5V input for high-performance microprocessors, which require significant current at the lower voltage. It explains that while linear regulators are preferred for minimizing components in line-operated equipment, switching supplies are necessary for portable computers where efficiency is paramount.
The note details specific circuit designs categorized by regulation type (linear and switching) and current capability. It covers component selection, including low dropout linear regulators like the LT1083/4/5/6 series and high-efficiency step-down switching regulators. The text also addresses critical design considerations such as controlling transient loads with bypass capacitors and thermal management through heat sinking.
The switch must be ON for two-thirds of each cycle and OFF for one-third.
The power dissipated can be as high as 8.5W.
The heat sink must have a thermal resistance of 6°C/W or less.