General Description

The MAX1774 is a complete power-supply solution for

PDAs and other hand-held devices. It integrates two

high-efficiency step-down converters, a boost converter

for backup battery regulation, and four voltage detec-

tors in a small 32-pin QFN or 28-pin QSOP package.

The MAX1774 accepts inputs from +2.7V to +28V and

provides an adjustable main output from 1.25V to 5.5V

at over 2A. The secondary core converter delivers an

adjustable voltage from 1V to 5V and can deliver up to

1.5A. Both the main and core regulators have separate

shutdown inputs.

When the AC adapter power is removed, an external P-

channel MOSFET switches input to the main battery.

When the main battery is low, the backup step-up con-

verter sustains the main output voltage. When the back-

up battery can no longer deliver the required load, the

system shuts down safely to prevent damage. Four on-

board voltage detectors monitor the status of the AC

adapter power, main battery, and backup battery.

The MAX1774 evaluation kit is available to help reduce

design time.

________________________Applications

Hand-Held Computers

PDAs

Internet Access Tablets

POS Terminals

Subnotebooks

Features

o Dual, High-Efficiency, Synchronous-Rectified

Step-Down Converters

o Thin, Small (1mm High) QFN Package

o Step-Up Converter for Backup Battery

o Main Power

Adjustable from +1.25V to +5.5V

Over 2A Load Current

Up to 95% Efficiency

o Core Power

Adjustable from 1V to 5V

Internal Switches

Up to 1.5A Load Current

Up to 91% Efficiency

o Automatic Main Battery Switchover

o 100% (max) Duty Cycle

o Up to 1.25MHz Switching Frequency

o Input Voltage Range from +2.7V to +28V

o Four Low-Voltage Detectors

o 170µA Quiescent Current

o 8µA Shutdown Current

o Digital Soft-Start

o Independent Shutdown Inputs

Dual, High-Efficiency, Step-Down

Converter with Backup Battery Switchover

________________________________________________________________ Maxim Integrated Products

1

17

18

19

20

21

22

23

N.C.

GND

GND

GND

GND

FBM

CS+

CS-

FBC

GND

INC

8

7

6

5

4

3

2

CVH

PDRV

IN

CVL

NDRV

PGND

PGNDC

MAX1774

32 7mm x 7mm QFN

1

MDRV

24

ACO

TOP VIEW

Pin Configurations

19-1810; Rev 1; 1/02

EVALUATION

KIT

AVAILABLE

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

MAX1774EEI

-40°C to +85°C

28 QSOP

MAX1774EMJ

-40°C to +85°C

32 7mm x 7mm QFN

AC

ADAPTER

MAIN

BATTERY

BACKUP

BATTERY

MAIN (+3.3V)

CORE (+1.8V)

AC OK

LOW MAIN BATTERY

DEAD MAIN BATTERY

MAX1774

Functional Diagram

Pin Configurations continued at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.