User Manual

EP7309/11/12 User’s Manual - DS508UM4 12-1

1212

Chapter 12

12PWM Interface

Introduction

There are two PW M (Pulse Width Modulator) outputs. This was designed for DC to

DC conversion circuits bu t can be used for other type s of controls. Typical use

includes backlight voltage for LCDs and programmable LCD contrast voltages.

Features

• Operates from Internal PLL or external 13 MH z clock

• Programmable duty cycle

• Feedback circuit control

• Power monitor for external AC or b attery use

Block Diagram

The block diagram below illustrates a typical design using both PWM drives in a

power supply.

V-

V+

VDD

FB1

V-

V+

VDD

FB0

V+

Vref

Comparator

DC-DC Circuit

PWM Drive0

PWM Drive1

V-

10K

VDD

GND

10K

Figure 12-1. Block Diagram of a Power Supply Using Two PWM Drives