Application Report

SLVA340A – June 2009 – Revised May 2010

High-Integration, High-Efficiency Power Solution Using

DC/DC Converters With DVFS

Ambreesh Tripathi

ABSTRACT

This

reference

design

helps

those

desiring

to

design-in

the

TMS320C6742,

TMS320C6746,

TMS320C6748 and OMAP-L138. This design, employing sequenced power supplies, describes a system

with an input voltage of 5V, and uses a high-efficiency DC/DC Converter with integrated FETs and DVFS

for a small, simple system.

Sequenced power supply architectures are becoming commonplace in high-performance microprocessor

and digital signal processor (DSP) systems. To save power and increase processing speeds, processor

cores have small-geometry cells that require lower supply voltages than the system-bus voltages. Power

management in these systems requires special attention. This application note addresses these topics

and suggests solutions for output-voltage sequencing.

Contents

1

Introduction

.................................................................................................................. 1

2

Power Requirements

....................................................................................................... 2

3

Features

...................................................................................................................... 3

4

List of Material

............................................................................................................... 5

List of Figures

1

PMP4977 Reference Design Schematic

................................................................................. 4

2

Optional circuit for DVDD_A, DVDD_B and DVDD_C

................................................................. 5

3

Shows Sequencing in Start-Up Waveform

.............................................................................. 7

4

DCDC1: Efficiency vs Output Current

.................................................................................... 7

5

DCDC2: Efficiency vs Output Current

.................................................................................... 7

6

DCDC3: Efficiency vs Output Current

.................................................................................... 7

List of Tables

1

PMP4977 List of Material

.................................................................................................. 5

1

Introduction

In dual-voltage architectures, coordinated management of power supplies is necessary to avoid potential

problems and ensure reliable performance. Power supply designers must consider the timing and voltage

differences between core and I/O voltage supplies during power-up and power-down operations.

Sequencing refers to the order, timing and differential in which the two voltage rails are powered up and

down. A system designed without proper sequencing may be at risk for two types of failures. The first of

these represents a threat to the long term reliability of the dual-voltage device, while the second is more

immediate, with the possibility of damaging interface circuits in the processor or system devices such as

memory, logic or data-converter ICs.

I

1

SLVA340A – June 2009 – Revised May 2010

High-Integration, High-Efficiency Power Solution Using DC/DC Converters With

DVFS

Copyright © 2009–2010, Texas Instruments Incorporated