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Application Report

SNVA211B–January 2007–Revised April 2013

AN-1571 Quick Start Guide for a 1.5 Amp Buck Regulator

Using the LM5575 and LM25575

.....................................................................................................................................................

ABSTRACT

This application note provides an easy to use process to help users design a 1.5 Amp buck regular using

the LM5575 and LM25575 switching regulators.

Contents

1 Introduction .................................................................................................................. 2

2 Quick Guide Design Worksheet ........................................................................................... 2

List of Figures

1 Application Schematic...................................................................................................... 2

List of Tables

1 Bill of Materials .............................................................................................................. 5

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SNVA211B–January 2007–Revised April 2013 AN-1571 Quick Start Guide for a 1.5 Amp Buck Regulator Using the LM5575

and LM25575

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Summary of content (6 pages)

PAGE 1
Application Report SNVA211B – January 2007 – Revised April 2013 AN-1571 Quick Start Guide for a 1.5 Amp Buck Regulator Using the LM5575 and LM25575 ..................................................................................................................................................... ABSTRACT This application note provides an easy to use process to help users design a 1.5 Amp buck regular using the LM5575 and LM25575 switching regulators. 1 2 Contents Introduction ...........................
PAGE 2
Introduction 1 www.ti.com Introduction The LM5575 and LM25575 switching regulators feature all of the functions necessary to implement an efficient high voltage buck regulator using a minimum of external components. These easy to use regulators include either a 42V (LM25575) or a 75V (LM5575) N-Channel buck switch with an output current capability of 1.5 Amps. The operating frequency is programmable from 50kHz up to 1MHz.
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Quick Guide Design Worksheet www.ti.com Step 3. Selection of the operating frequency is a trade-off between the conversion efficiency and solution size. Operating at a high frequency, with a relatively high input voltage will severely impact the efficiency and consequently generate a lot of heat. In some applications, the selection of a high operating frequency will limit the input voltage range. The recommended maximum operating frequency for applications using LM5575 is 500 KHz.
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Quick Guide Design Worksheet www.ti.com Calculate the value of Rfb1: Rfb1 = 1.225 x Rfb2[9] (Vout[1] ± 1.225) (6) Selected value of Rfb1: Ohms [10] Step 8. Select the re-circulating diode, D1. A Schottky type diode is required for all applications. Ultra-fast diodes are not recommended and may result in damage to the IC due to reverse recovery current transients.
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Quick Guide Design Worksheet www.ti.com Calculate the value of Ccomp Ccomp = 1 8 x 103 x Rcomp[14] Selected value of Ccomp: (10) Farads [15] Step 12. Shown in Table 1 is the Bill of Materials for your design. Transcribe each value [#] from the worksheet above into the following table. Congratulations, you’re done. 2.1 Bill of Materials Table 1.
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