Compact, 1.5 A Linear Charger
for Single-Cell Li+ Battery
ADP2291
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
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.
APPLICATIONS
Wireless handsets
Smart handhelds and PDAs
Digital cameras
Single-cell, lithium ion-powered systems
Cradle chargers
TYPICAL OPERATING CIRCUIT
INPUT
4.6V–12V
CIN
CS
IN
DRV
BAT
RS
Q1
+
COUT
ADP2291
CHG
TIMER
CTIMER
ADJ
04873-001
GND
SHUTDOWN
Figure 1.
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.
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Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
© 2005 Analog Devices, Inc. All rights reserved.
ADP2291
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Typical Operating Circuit................................................................ 1
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Pin Configurations and Function Descriptions ........................... 6
Typical Performance Characteristics ............................................. 7
Theory of Operation ...................................................................... 10
Precharge Mode.......................................................................... 10
End-of-Charge Mode................................................................. 10
Shutdown Mode.......................................................................... 10
Charge Restart............................................................................. 10
Programmable Timer................................................................. 10
Charge Status Indicator ............................................................. 10
Automatic Reverse Isolation ..................................................... 10
Overshoot Protection................................................................. 10
Power Supply Checks................................................................. 10
Thermal Shutdown .................................................................... 11
Application Information................................................................ 12
Setting the Maximum Charge Current.................................... 12
Setting the Maximum Charge Time ........................................ 12
External Capacitors.................................................................... 12
Reverse Input Protection........................................................... 12
External Pass Transistor ............................................................ 13
Typical Application Circuit....................................................... 14
Charge Termination................................................................... 14
Selectable Charge Current......................................................... 14
Thermal Protection.................................................................... 14
Printed Circuit Board Layout Considerations ....................... 16
LFSCP Layout Considerations.................................................. 16
Outline Dimensions ....................................................................... 17
Ordering Guide .......................................................................... 17
REVISION HISTORY
11/05—Rev. 0 to Rev. A
Changes to Equation 7 ................................................................... 13
Changes to Figure 26...................................................................... 15
Changes to Table 7.......................................................................... 16
Changes to Ordering Guide .......................................................... 17
Updated Outline Dimensions ....................................................... 17
10/04—Initial Version: Revision 0
Rev. A | Page 2 of 20
ADP2291
SPECIFICATIONS
V
IN
= 5.5 V, V
BAT
= 4.2 V, R
ADJ
open, T
A
= –40°C to +85°C, typical values are at 25°C, unless otherwise noted.
1
Table 1.
Parameter
POWER SUPPLY, IN
Input Voltage
Current Draw
BATTERY VOLTAGE, BAT
Voltage Accuracy, End-of-Charge (V
BAT, EOC
)
Conditions
Min
4.5
Fast charge/precharge/end-of-charge modes
Timeout/shutdown/battery fault
T
A
= 0°C to +50°C
V
IN
= 4.5 V to 12 V
V
IN
– V
CS
= VRS/10
V
IN
– V
CS
= 0 to VRS
Timeout mode, V
IN
= 4.5 V to 12 V
Battery fault/shutdown mode, V
IN
= 4.5 V to 12 V
Power-down mode: V
IN
= float, V
BAT
= 4.2 V
V
IN
– V
CS
, R
ADJ
= open
V
IN
= 4.5 V to 12 V
V
BAT
= 3.6 V
V
IN
– V
CS
, R
ADJ
= 100 kΩ
V
IN
= 4.5 V to 12 V
V
BAT
= 3.6 V
Per V of (3 V – V
ADJ
)
V
IN
– V
CS,
R
ADJ
= open
V
IN
= 4.5 V to 12 V
V
BAT
= 2 V
V
IN
– V
CS
, R
ADJ
= 100 kΩ
V
IN
= 4.5 V to 12 V
V
BAT
= 2 V
V
BAT
rising
4.158
6
1.4
4.2
Typ
Max
12
9
1.8
4.242
Unit
V
mA
mA
V
Load Regulation, No Battery
Current Draw
Current Draw
Reverse Leakage Current
FAST CHARGE MODE
Sense Voltage Setpoint (VRS)
−80
0.1
0.1
140
150
45
1
mV
µA
µA
µA
mV
160
Sense Voltage Setpoint (VRS)
40
50
60
mV
Current Regulation Adjustment
PRECHARGE MODE
Sense Voltage Setpoint (VRS)
67
10
15
20
mV/V
mV
Sense Voltage Setpoint (VRS)
5
10
15
mV
BAT Precharge Threshold
Hysteresis
SHUTDOWN MODE
ADJ Shutdown Threshold
Hysteresis
Pull-Up Current from ADJ
POWER-DOWN MODE
V
IN
Power-Down Threshold
Hysteresis
V
IN
_Good Comparator
Threshold (V
IN
> V
BAT
)
Hysteresis
EOC COMPARATOR
Current Threshold
Current Threshold
Hysteresis
RESTART COMPARATOR
BAT Restart Threshold
2.65
70
2.85
V
mV
V
mV
µA
V
mV
mV
mV
%
%
mV
mV
V
ADJ
falling, V
IN
= 4.5 V
V
ADJ
= 0
V
IN
rising
0.30
40
40
3.6
220
0.45
4
V
IN
rising
125
170
110
10
10
12
220
V
IN
– V
CS
falling, R
ADJ
= open, relative to VRS
V
IN
– V
CS
falling, R
ADJ
= 100 kΩ, relative to VRS
7
6
13
16
V
IN
> 4.5 V, V
BAT
falling, relative to V
BAT, EOC
−170
Rev. A | Page 3 of 20
ADP2291
Parameter
BATTERY CHARGE TIMER
Charge/Discharge TIMER Current
Low Threshold
High Threshold
High-Low Threshold Delta
2
OVERSHOOT PROTECTION
BAT Threshold
Current Sink
CHG OUTPUT
Output Voltage Low
Output Leakage Current
BASE DRIVE CAPABILITY
Maximum Base Drive Current
THERMAL SHUTDOWN
Shutdown Threshold
Hysteresis
1
2
Conditions
Min
21.0
Typ
24.0
1.2
2.0
Max
27.0
Unit
µA
V
V
mV
V
A
V
µA
mA
750
4.7
<2 ms duration
Current = 20 mA
V
CHG
= 5 V
40
T
A
rising
135
35
5
1.5
850
5.3
0.1
0.45
1
°C
°C
All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC). Typical values are at T
A
= 25°C.
Guaranteed by design; not tested in production.
Rev. A | Page 4 of 20
ADP2291
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
IN, DRV,
1
CS, CHG to GND
BAT, ADJ, TIMER to GND
Operating Ambient Temperature
Operating Junction Temperature
θ
JA
, 2-layer MSOP-8
θ
JA
, 4-layer MSOP-8
θ
JA
, 2-layer LFCSP-8
θ
JA
, 4-layer LFCSP-8
Storage Temperature
Range
Lead Temperature Soldering (10 sec)
1
Rating
−0.3 V to +13.5 V
−0.3 V to (V
IN
+ 0.3 V)
−40°C to +85°C
−40°C to +125°C
220ºC/W
158ºC/W
62ºC/W
48ºC/W
−65°C to +150°C
300°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other condition s above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Absolute maximum ratings apply individually only, not in
combination. Unless otherwise specified all other voltages
referenced to GND.
Pulling current from the DRV pin by driving it below ground while VIN is
applied can cause permanent damage to the device.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. A | Page 5 of 20
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