Rainbow-electronics MAX1774 Bedienungsanleitung PDF herunterladen

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

♦ 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

MAX1774

Dual, High-Efficiency, Step-Down

Converter with Backup Battery Switchover

________________________________________________________________ Maxim Integrated Products 1

BKUP

SHDNC

SHDNM

N.C.

LXC

INS

LBO

25 N.C.

LXB

LXB2

BIN

BKOFF

ACI

DBI

LBI

16REF

N.C.

GND

FBM

CS+

CS-

FBC

GND

INC

CVH

PDRV

CVL

NDRV

PGND

PGNDC

MAX1774

32 7mm x 7mm QFN

1MDRV

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

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.

1 2 3 4 5 6 ... 20 21

Inhaltsverzeichnis

Seite 1 - TOP VIEW

General DescriptionThe MAX1774 is a complete power-supply solution forPDAs and other hand-held devices. It integrates twohigh-efficiency step-down con

Seite 2 - ELECTRICAL CHARACTERISTICS

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover10 ___________________________________________________________________

Seite 3

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 4

each cycle (see Typical Operating Characteristics). Theswitch waveform may exhibit ringing, which occurs atthe resonant frequency of the inductor and

Seite 5

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 6

The MAX1774 features four separate current-limitthreshold detectors and a watchdog timer for each of itsstep-down converters. In addition to the more

Seite 7

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 8 - = +3.3V, T

Place 1MΩ pullup resistors from the main output toACO, LBO, and BKUP. Use a 1MΩ pullup resistor fromMDRV to IN.When not in backup mode, the backup reg

Seite 9

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 10 - Pin Description

nals, and be close together to improve noise rejection.These traces should be used for current-sense signalrouting only and should not carry any load

Seite 11 - Pin Description (continued)

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 12 - 100% Duty Cycle and Dropout

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover2 ____________________________________________________________________

Seite 13 - Regulation Control Scheme

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover20 ___________________________________________________________________

Seite 14 - Core Step-Down Converter

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses arei

Seite 15

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 16 - Design Procedure

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover4 ____________________________________________________________________

Seite 17 - Setting the Current Limit

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 18

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover6 ____________________________________________________________________

Seite 19 - Chip Information

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

Seite 20 - Package Information

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover8 ____________________________________________________________________

Seite 21 - QSOP.EPS

MAX1774Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover______________________________________________________________________

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Inhaltsverzeichnis

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