Final Electrical Specifications
LTC1732-4/LTC1732-4.2
Lithium-Ion Linear
Battery Charger Controller
FEATURES
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DESCRIPTIO
October 2000
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Complete Linear Charger Controller for 1-Cell
Lithium-Ion Batteries
Preset Charge Voltage with 1% Accuracy
4.5V to 12V Input Voltage Range
Programmable Charge Current
C/10 Charge Current Detection Output
Programmable Charge Termination Timer
Small, Thin 10-Pin MSOP Package
Select Pin to Charge Either 4.1V or
4.2V Cells (LTC1732-4)
Automatic Sleep Mode When Input Supply
is Removed (Only 7µA Battery Drain)
Automatic Trickle Charge of Low Voltage Cells
Programmable for Constant-Current-Only Mode
Battery Insertion Detect and Automatic Charging
of Low-Battery Cell
Input Supply (Wall Adapter) Detection Output
4.05V Recharge Threshold for 4.2V Cells
(LTC1732-4.2)
3.8V Recharge Threshold for 4.1V or 4.2V Cells
(LTC1732-4)
The LTC
®
1732 is a complete constant-current/constant-
voltage linear charge controller for lithium-ion
(Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metal-
hydride (NiMH) batteries can also be charged with con-
stant current using external termination. Charge current
can be programmed with 7% (max) accuracy using exter-
nal sense and program resistors. An internal resistor
divider and precision reference set the final float voltage
with 1% accuracy. The SEL pin allows users to charge
either 4.1V or 4.2V cells.
When the input supply is removed, the LTC1732 automati-
cally enters a low current sleep mode, dropping the battery
drain current to 7µA. An internal comparator detects the
end-of-charge (C/10) condition while a programmable
timer, using an external capacitor, sets the total charge
time. Fully discharged cells are automatically trickle charged
at 10% of the programmed current until cell voltage
exceeds 2.457V.
The LTC1732 begins a new charge cycle when a discharged
battery is connected to the charger or when the input power
is applied. In addition, if the battery remains connected to
the charger and the cell voltage drops below 3.8V for the
LTC1732-4 or below 4.05V for the LTC1732-4.2, a new
charge cycle will begin.
The LTC1732 is available in the 10-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIONS
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Cellular Phones
Handheld Computers
Charging Docks and Cradles
TYPICAL APPLICATION
Single Cell 4.2V Li-Ion Battery Charger
V
IN
= 6V
MBRM120T3
R2
1k
R1
1k
3
8
V
CC
2
SEL
SENSE
CHRG
DRV
9
7
R
SENSE
0.2Ω
Q1
Si9430DY
I
BAT
= 500mA
1µF
LTC1732-4
10
4
C
TIMER
0.1µF
ACPR
TIMER
BAT
PROG
1
6
R
PROG
*
19.6k
GND
5
10µF
+
4.2V
Li-Ion
CELL
1732 TA01
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LINER [ LINEAR TECHNOLOGY ]
