MAX1774 데이터 시트보기 (PDF) - Maxim Integrated

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MAX1774

Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover

Maxim Integrated 

19-1810; Rev 2; 12/03

EVAALVUAAILTAIOBNLEKIT

Dual, High-Efficiency, Step-Down

Converter with Backup Battery Switchover

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

Pin Configurations

TOP VIEW

GND

GND

MDRV 1

PGNDC 2

PGND 3

NDRV 4

CVL 5

IN 6

PDRV 7

CVH 8

MAX1774

24 ACO

23 INC

22 GND

21 FBC

20 CS-

19 CS+

18 FBM

17 N.C.

GND

GND

Features

♦ Dual, High-Efficiency, Synchronous-Rectified

Step-Down Converters

♦ Thin, Small (1mm High) QFN Package

♦ Step-Up Converter for Backup Battery

♦ Main Power

Adjustable from +1.25V to +5.5V

Over 2A Load Current

Up to 95% Efficiency

♦ Core Power

Adjustable from 1V to 5V

Internal Switches

Up to 1.5A Load Current

Up to 91% Efficiency

♦ Automatic Main Battery Switchover

♦ 100% (max) Duty Cycle

♦ Up to 1.25MHz Switching Frequency

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

♦ Four Low-Voltage Detectors

♦ 170µA Quiescent Current

♦ 8µA Shutdown Current

♦ Digital Soft-Start

♦ Independent Shutdown Inputs

Ordering Information

PART

MAX1774EEI

MAX1774EGJ

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

PIN-PACKAGE

28 QSOP

32 7mm x 7mm QFN

Functional Diagram

AC

ADAPTER

MAIN

BATTERY

BACKUP

BATTERY

MAX1774

MAIN (+3.3V)

CORE (+1.8V)

AC OK

LOW MAIN BATTERY

DEAD MAIN BATTERY

32 7mm x 7mm QFN

Pin Configurations continued at end of data sheet.

________________________________________________________________ Maxim Integrated Products 1

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.

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