_______________General Description

The MAX747 high-efficiency, high-current, step-down

controller drives external P-channel FETs. It provides

90% to 95% efficiency from a 6V supply with load

currents ranging from 50mA up to 2.5A. It uses a

pulse-width-modulating (PWM) current-mode control

scheme to provide precise output regulation and low

output noise. The MAX747’s 4V to 15V input voltage

range, a fixed 5V/adjustable (Dual-Mode™) output, and

a current limit set with an external resistor make this

device ideal for a wide range of applications.

High efficiency is maintained with light loads due to a

proprietary dual-control (Idle-Mode™) scheme that

minimizes switching losses by reducing the switching

frequency at light loads. The low 800µA quiescent

current and ultra-low 0.6µA shutdown current further

extend battery life.

External components are protected by the MAX747’s

cycle-by-cycle current limit. The MAX747 also features a

2V ±1.5% reference, a comparator for low-battery

detection or level translating, as well as soft-start and

shutdown capability.

The MAX746, discussed in a separate data sheet,

functions similarly to the MAX747, but it drives N-channel

logic level FETs on the high side.

________________________Applications

Notebook Power Supplies

Personal Digital Assistants

Battery-Operated Equipment

Cellular Phones

5V to 3.3V Green PC Applications

____________________________Features

o 90% to 95% Efficiency for 50mA to 2.5A

Output Currents

o 4V to 15V Input Voltage Range

o Low 800µA Supply Current

o 0.6µA Shutdown Current

o Drives External P-Channel FETs

o Cycle-by-Cycle Current Limiting

o 2V ±1.5% Accurate Reference Output

o Adjustable Soft-Start

o Precision Comparator for Power-Fail or

Low-Battery Warning

______________Ordering Information

* Contact factory for dice specifications.

High-Efficiency PWM, Step-Down

P-Channel DC-DC Controller

________________________________________________________________

Maxim Integrated Products

1

OUTPUT

5V

2.3A

INPUT

6V TO 15V

AV+

EXT

OUT

GND

430µF

REF

MAX747

CS

SHDN

ON/OFF

LBI

LOW-BATTERY

DETECTOR

INPUT

V+

LOW-BATTERY

DETECTOR

OUTPUT

AGND

FB

CC

SS

LBO

5Om

Ω

5O

µH

P

0.1µF

100µF

__________________Pin Configuration

SS

1

2

3

4

14

13

12

11

GND

CC

FB

AV+

LBI

DIP/SO

TOP VIEW

MAX747

5

6

7

10

9

8

OUT

AGND

REF

SHDN

LBO

V+

EXT

CS

__________Typical Operating Circuit

Call toll free 1-800-998-8800 for free samples or literature.

19-0171; Rev 1; 9/93

PART

TEMP. RANGE

PIN-PACKAGE

MAX747CPD

0°C to +70°C

14 Plastic DIP

MAX747CSD

0°C to +70°C

14 Narrow SO

MAX747C/D

0°C to +70°C

Dice*

MAX747EPD

-40°C to +85°C

14 Plastic DIP

MAX747ESD

-40°C to +85°C

14 Narrow SO

MAX747MJD

-55°C to +125°C

14 CERIDIP

™ Dual-Mode and Idle-Mode are trademarks of Maxim Integrated Products.