Texas Instruments SLVP089 User Manual

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SLVP089 Synchronous Buck

Converter Evaluation Module

User’s Guide

1998

Mixed-SignalLinear Products

 

 

 

 

 

 

 

 

 

Printed in U.S.A.

SLVU001A

07/98

 

 

SLVP089 Synchronous Buck

Converter Evaluation Module

User’s Guide

Literature Number: SLVU001A

July 1998

Printed on Recycled Paper

IMPORTANT NOTICE

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TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.

CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORTDEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER’S RISK.

In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI’s publication of information regarding any third party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.

Copyright 1998, Texas Instruments Incorporated

Related Documentation From Texas Instruments

Preface

Read This First

About This Manual

This user’s guide is a reference manual for the SLVP089 Synchronous Buck Converter Evaluation Module used to evaluate the performance of the TL5001 PWM Controller. This document provides information to assist managers and hardware engineers in application development.

How to Use This Manual

This manual provides the information and instructions necessary to design, construct, operate, and understand the SLVP089. Chapter 1 describes and lists the hardware requirements; Chapter 2 describes design considerations and procedures; and Appendix A contains the data sheet for the TL5001 PWM Controller

Related Documentation From Texas Instruments

The following books describe the TL5001 and related support tools. To obtain a copy of any of these TI documents, call the Texas Instruments Literature Response Center at (800) 477–8924.When ordering, please identify the book by its title and literature number.

TL5001 Pulse-Width-ModulationControl Circuits Data Sheet(Literature number SLVS084C). It contains electrical specifications, available temperature options, general overview of the device, and application information.

Designing with the TL5001C PWM Controller Application Report

(Literature number SLVA034).

Read This First

iii

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2)Please mention the full title of the book, the literature number from the lower-rightcorner of the back cover, and the publication date from the spine or front cover.

FCC Warning

This equipment is intended for use in a laboratory test environment only. It generates, uses, and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to subpart J of part 15 of FCC rules, which are designed to provide reasonable protection against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case the user at his own expense will be required to take whatever measures may be required to correct this interference.

Trademarks

TI is a trademark of Texas Instruments Incorporated.

iv

Running Title—AttributeReference

Contents

1 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.2 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.3 Input/Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1.4 Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

1.5 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

1.6 Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

2 Design Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-1

2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2

2.2

Operating Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-3

2.3

Design Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-4

 

2.3.1

Duty Cycle Estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-4

 

2.3.2

Output Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-4

 

2.3.3

Power Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-4

 

2.3.4 Synchronous Switch and Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-5

 

2.3.5

Snubber Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-5

 

2.3.6

Controller Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-5

 

2.3.7

Loop Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-6

Chapter Title—AttributeReference

v

Running Title—AttributeReference

Figures

1–1Typical Synchronous Buck Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-21–2Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-41–3Input/Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-51–4Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-61–5Efficiency Vs Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-81–6Power SwitchTurn-Onand Delay from Q2 Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-91–7Power SwitchTurn-Offand Delay to Q2 On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-91–8Inductor and Output Ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-102–1Power Stage Bode Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72–2Compensation Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72–3Bode Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-82–4Output Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

Tables

1–1

Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

1–2

Line/Load Regulation, 3.3-V(Total Variation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-8

1–3

Load Regulation and Ripple, 3.3-V(9-VInput) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-8

2–1

Operating Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-3

vi

Chapter 1

Hardware

The SLVP089 Synchronous Buck Converter Evaluation Module (SLVP089) provides a method for evaluating the performance of the TL5001 pulse-width-modulation (PWM) controller. The device contains all of the circuitry necessary to control aswitch-modepower supply in avoltage-modeconfiguration. This manual explains how to construct basic power conversion circuits including the design of the control chip functions and the basic loop. This chapter includes the following topics:

Topic

 

Page

 

 

 

1.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 1–2

1.2

Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 1–3

1.3

Input/Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1–5

1.4

Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1–6

1.5

Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1–7

1.6

Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1–8

 

 

 

Chapter Title—AttributeReference

1-1

Introduction

1.1 Introduction

Synchronous buck converters provide the smaller size and higher efficiency required by electronic equipment, particularly portable battery-operatedequipment. The synchronous buck converter reduces power losses associated with a standard buck converter by substituting a power MOSFET for the commutating diode. This reduces the typical0.5-Vto1-Vdiode drop to 0.3 V or less and increases system efficiency by up to 10 percent.Continuous-currentmode is desirable and is used in this EVM for the lowpeak-to-averagecurrent ratio. Figure1–1shows a typical synchronous buck converter.

Figure 1–1.Typical Synchronous Buck Converter

VI

 

R3

+

 

 

 

 

 

 

C1

 

 

 

Q1

 

 

 

L1

 

R1

 

 

VO

Controller

 

 

 

Q2

 

 

 

 

 

FB

 

+

R2

 

CR1

C2

 

 

 

 

R4

 

 

Transistor Q1 is the power switch and Q2 is the synchronous switch. A diode in parallel with Q2 allows inductor current flow during the dead time when both transistors are turned off. If dead time is not present in this configuration, high transient shoot-throughcurrents will flow during the transition when one transistor is turning on and the other is turning off, usually resulting in destruction of the power stage switches.

The SLVP089 evaluation module will supply a nominal 3.3-Voutput over a load range from 0 to 3 A using a dc input voltage of 5.5 V to 12 V. Full load efficiency is typically 90 percent.

1-2