Dual-Output Step-Down and LCD Step-Up

Power Supply for PDAs

________________________________________________________________ Maxim Integrated Products

1

19-2248; Rev 1; 12/03

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.

General Description

The MAX1878 dual power supply contains a step-down

and step-up DC-DC converter in a small 12-pin QFN

package for use in PDAs. The step-down DC-DC convert-

er delivers over 500mA to an output as low as 1.25V for

logic power. The step-up DC-DC converter delivers over

15mA and an output as high as 28V for a liquid crystal dis-

play (LCD). With an input voltage from 2.0V to 5.5V the

MAX1878 is intended for use in systems powered by a

2-cell alkaline or 1-cell lithium-ion (Li+) battery.

Fast switching frequency allows the use of small inductors

and capacitors, and the low 19µA typical quiescent cur-

rent allows high efficiency when the system is in standby

mode. Each output can be independently enabled.

The MAX1878 is available in a small 1mm high 4mm x

4mm 12-pin QFN package and requires no external FETs.

The MAX1878 evaluation kit is available to speed designs.

________________________Applications

Personal Digital Assistants (PDA)

Organizers/Translators

MP3 Players

GPS Receivers

Features

♦ Evaluation Kit Available to Speed Designs

♦ Two Output Voltages

LCD Output: Up to 28V

♦ 2.0V to 5.5V Input Range

♦ Low 19µA Quiescent Supply Current

♦ 1µA Shutdown Supply Current

♦ High Switching Frequency for Small External

Components

♦ Small 1mm High 4mm x 4mm 12-Pin QFN Package

Pin Configuration

MAX1878

INPUT

2.0V TO 5.5V

ON

ON

OFF

OFF

MAIN

LCD

LCD OUTPUT

UP TO 28V

MAIN OUTPUT

10µH

IN

AIN1

AIN2

ON

ONLCD

PGND

AGND PGNDLCD

FB

LX

FBLCD

LXLCD

0.1µF

10µH

__________Typical Operating Circuit

EVALUATION

KIT

AVAILABLE

PART

TEMP RANGE

PIN-

PACKAGE

TOP

MARK

MAX1878EGC

-40°C to +85°C

12-QFN

AAAO

Ordering Information

12

11

10

9

LXLCD

8AGND

7ON

4

5

6

1

IN

2

LX

3

AIN1

MAX1878EGC

4mm x 4mm QFN

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