Rainbow-electronics MAX1874 Manual do Utilizador descarregar pdf

General Description

The MAX1874 charges a single-cell Li+ battery from

both USB and AC adapter sources. It also includes bat-

tery-to-input power switchover, so the system can be

powered directly from the power source rather than

from the battery.

In its simplest application, the MAX1874 needs no

external MOSFET or diodes, and accepts input volt-

ages up to 6.5V; however, DC input overvoltage protec-

tion up to 18V can be added with a single SOT PFET.

On-chip thermal limiting simplifies PC board layout and

allows optimum charging rate without the thermal limits

imposed by worst-case battery and input voltage. When

the MAX1874 thermal limit is reached, the charger does

not shut down but simply reduces charging current.

Ambient or battery temperature can be monitored with

an external thermistor. When the temperature is out of

range, charging pauses.

Other features include a CHG output to indicate when

battery current tapers below a predetermined level. DC

power-OK (DCOK), USB power-OK (UOK), and power-

on (PON) outputs indicate when valid power is present.

These outputs drive logic or power-selection MOSFETs

to disconnect the charging sources from the load and

to protect the MAX1874 from overvoltage.

The MAX1874 contains no logic for communication with

the USB host. It must receive instructions from a local

microcontroller. The MAX1874 is available in a 16-pin

5mm ✕ 5mm thin QFN package and operates over the

-40°C to +85°C temperature range.

Applications

PDAs Cell Phones

Wireless Appliances Digital Cameras

Features

♦ Charge from USB* or AC Adapter

♦ Automatic Switchover to AC Adapter

♦ Thermal Limiting Simplifies Board Design

♦ Small, High-Power 16-Pin Thin QFN Package

♦ Input Protection Up to 18V

♦ Soft-Start

♦ Automatic Battery-to-Input Load Switch

*Protected by U.S. Patent #6,507,172.

MAX1874

Dual-Input, USB/AC Adapter, 1-Cell

Li+ Charger with OVP and Thermal Regulation

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-2912; Rev 0; 7/03

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.

PART TEMP RANGE PIN-PACKAGE

MAX1874ETE -40°C to +85°C 16 Thin QFN 5mm x 5mm

16 15 14 13

DCOK

BATT

PON

UOK

REF

PGND

BYP

USB

USEL

CHG

DCLV

5678

GND

DCI

THRM

MAX1874

THIN QFN

5mm x 5mm

TOP VIEW

Pin Configuration

Functional Diagram appears at the end of the data sheet.

MAX1874

USB INPUT

DC INPUT

TO REF

DCLV

GND

BATT

NTC

THERMISTOR

PON

REF

THRM

USB

Li+

CELL

USEL

500mA

100mA

ENDCI

PGND

BYP

REGULATOR

UOK

CHG

DCOK

Typical Operating Circuit

1 2 3 4 5 6 ... 15 16

Resumo do Conteúdo

Página 1 - PART TEMP RANGE PIN-PACKAGE

General DescriptionThe MAX1874 charges a single-cell Li+ battery fromboth USB and AC adapter sources. It also includes bat-tery-to-input power switcho

Página 2 - ELECTRICAL CHARACTERISTICS

MAX1874Detailed DescriptionThe MAX1874 charges a single-cell Li+ battery fromeither USB power sources or AC adapter sources. Itcontains a complete two

Página 3

acceptable range. To verify that the input voltage is stable, DCOK has an internal delay of 20ms before con-necting power to DCLV. DCOK remains operat

Página 4

MAX1874The MAX1874’s thin QFN package includes a bottommetal plate that reduces thermal resistance between thedie and the PC board. The external pad s

Página 5