Compact, 1.5 A Linear Charger
for Single-Cell Li+ Battery
ADP2291
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.
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-lead 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 tem-
perature. 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-lead 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
.6V–12V
SHUTDOWN
+
IN
CHG
BAT
CIN
GND
CS DRV
COUT
04873-001
Figure 1.
