LT1511
Constant-Current/
Constant-Voltage 3A Battery
Charger with Input Current Limiting
DESCRIPTIO
U
FEATURES
s
s
s
s
s
s
s
s
s
s
s
The LT®1511 current mode PWM battery charger is the
simplest, most efficient solution to fast charge modern
rechargeable batteries including lithium-ion (Li-Ion), nickelmetal-hydride (NiMH) and nickel-cadmium (NiCd) that
require constant-current and/or constant-voltage charging. The internal switch is capable of delivering 3A* DC
current (4A peak current). Full-charging current can be
programmed by resistors or a DAC to within 5%. With 0.5%
reference voltage accuracy, the LT1511 meets the critical
constant-voltage charging requirement for Li-Ion cells.
Simple Design to Charge NiCd, NiMH and Lithium
Rechargeable Batteries—Charging Current
Programmed by Resistors or DAC
Adapter Current Loop Allows Maximum Possible
Charging Current During Computer Use
Precision 0.5% Accuracy for Voltage Mode Charging
High Efficiency Current Mode PWM with 4A Internal
Switch
5% Charging Current Accuracy
Adjustable Undervoltage Lockout
Automatic Shutdown When AC Adapter is Removed
Low Reverse Battery Drain Current: 3µA
Current Sensing Can Be at Either Terminal of the Battery
Charging Current Soft-Start
Shutdown Control
A third control loop is provided to regulate the current
drawn from the AC adapter. This allows simultaneous
operation of the equipment and battery charging without
overloading the adapter. Charging current is reduced to
keep the adapter current within specified levels.
The LT1511 can charge batteries ranging from 1V to 20V.
Ground sensing of current is not required and the battery’s
negative terminal can be tied directly to ground. A saturating switch running at 200kHz gives high charging efficiency and small inductor size. A blocking diode is not
required between the chip and the battery because the
chip goes into sleep mode and drains only 3µA when the
wall adapter is unplugged.
U
APPLICATIO S
s
s
Chargers for NiCd, NiMH, Lead-Acid, Lithium
Rechargeable Batteries
Switching Regulators with Precision Current Limit
, LTC and LT are registered trademarks of Linear Technology Corporation.
*See LT1510 for 1.5A Charger
U
TYPICAL APPLICATIO
R7†
500Ω
BOOST
LT1511
COMP1
L1**
20µH
D2
MBR0540T
CLN
VCC
SW
C2
0.47µF
D1
MBRD340
CLP
GND
200pF
+
+
10µF
RS4†
ADAPTER
CURRENT SENSE
CIN*
10µF
UV
VC
SPIN
RS3
200Ω
1%
BAT
RS2
200Ω
1%
RS1
0.033Ω
BATTERY CURRENT
SENSE
50pF
VIN (ADAPTER INPUT)
11V TO 28V
TO MAIN
SYSTEM POWER
R5†
UNDERVOLTAGE
LOCKOUT
R6
5k
PROG
OVP SENSE
NOTE: COMPLETE LITHIUM-ION CHARGER,
NO TERMINATION REQUIRED. RS4, R7
AND C1 ARE OPTIONAL FOR IIN LIMITING
*TOKIN OR UNITED CHEMI-CON/MARCON
CERAMIC SURFACE MOUNT
**20µH COILTRONICS CTX20-4
†SEE APPLICATIONS INFORMATION FOR
INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT
C1
1µF
D3
MBRD340
300Ω
1k
CPROG
1µF
RPROG
4.93k
1%
0.33µF
R3
390k
0.25%
BATTERY
VOLTAGE SENSE
+
COUT
22µF
TANT
+
4.2V
+
VBAT
2 Li-Ion
4.2V
1511 • F01
R4
162k
0.25%
Figure 1. 3A Lithium-Ion Battery Charger
1
