Compact, 1.5 A Linear Charger

for Single-Cell Li+ Battery

ADP2291

Rev. 0

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FEATURES

Simple, safe linear charger for single cell lithium battery

4.5 V to 12 V input voltage range

Adjustable charging current up to 1.5 A

Low cost PNP external pass element

Automatic reverse isolation with no external blocking diode

Output overshoot protection

Deep discharge precharge mode

Thermal shutdown

Automatic recharge

Programmable termination timer

LED charging status indicator

4.2 V output voltage with ±1% accuracy over line and

temperature

1 µA shutdown supply current

Small, 8-pin MSOP and 3 × 3 mm LFCSP packages

APPLICATIONS

Wireless handsets

Smart handhelds and PDAs

Digital cameras

Single cell lithium ion-powered systems

Cradle chargers

GENERAL DESCRIPTION

The ADP2291 is a constant-current/constant-voltage linear

charger for a single cell lithium ion battery, requiring just a few

components to provide a simple and safe charging system that

operates from a wide 4.5 V to 12 V input voltage range. It

features an internally controlled, multistep charging cycle that

improves battery life.

An external, low cost, PNP provides the charging current to the

battery and an external resistor sets the maximum charge

current. A small external capacitor programs the maximum

charge time. The controller includes an LED driver to indicate

the battery charging status.

Safety features include charging stop mode for battery faults,

output overshoot protection, and thermal shutdown. The

ADP2291 also features automatic reverse isolation, which does

not require an additional blocking diode.

The multistep charge cycle optimizes the battery charging time

in a safe manner. It features a trickle charge mode for a deeply

discharged cell and a fast charging mode with a maximum

current of 1.5 A. The ADP2291 controls the end of charge with

a 4.2 V output voltage that is 1% accurate over line and temp-

erature. It automatically recharges the battery if the cell voltage

drops. When the input supply is removed, the part enters a low

current state and reduces the current drawn from the battery to

below 1 µA.

The ADP2291 is available in both a small, 8-pin MSOP package

and a 3 × 3 mm LFCSP package that is ideally suited for small,

portable applications.

TYPICAL OPERATING CIRCUIT

ADP2291

TIMER

ADJ

RS

Q1

CTIMER

INPUT

4.6V–12V

SHUTDOWN

+

IN

CHG

BAT

CIN

GND

CS

DRV

COUT

Figure 1. Basic Circuit Configuration