LTC1731-8.2/LTC1731-8.4
Lithium-Ion Linear
Battery Charger Controller
FEATURES
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DESCRIPTIO
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Complete Linear Charger Controller for
2-Cell Lithium-Ion Batteries
1% Voltage Accuracy
Programmable Charge Current
C/10 Charge Current Detection Output
Programmable Charge Termination Timer
Space Saving 8-Pin MSOP Package
Automatic Sleep Mode When Input Supply
is Removed (15µA Battery Drain)
Automatic Trickle Charging of Low Voltage Cells
Programmable for Constant-Current-Only Mode
The LTC
®
1731-8.2/LTC1731-8.4 are complete constant-
current/constant-voltage linear charger controllers for 2-
cell lithium-ion (Li-Ion)batteries. Nickel-cadmium (NiCd)
and nickel-metal-hydride (NiMH) batteries can also be
charged with constant current using external termina-
tion. The external sense resistor sets the charge current
with 7% accuracy. An internal resistor divider and preci-
sion reference set the final float potential with 1% accu-
racy. The output float voltages are set internally to 8.2V
(LTC1731-8.2) or 8.4V (LTC1731-8.4).
When the input supply is removed, the LTC1731-8.2/
LTC1731-8.4 automatically enter a low current sleep mode,
dropping the battery drain current to typically 15µA. An
internal comparator detects the end-of-charge (C/10) con-
dition while a programmable timer, using an external
capacitor, sets the total charge time. Fully discharged cells
are automatically trickle charged at 10% of the pro-
grammed current until battery voltage exceeds 4.95V.
The LTC1731-8.2/LTC1731-8.4 are available in the 8-pin
MSOP and SO packages. For 1-cell Li-Ion battery charg-
ing, see the LTC1731-4.1 and LTC1731-4.2 data sheets.
APPLICATIO S
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Cellular Phones
Handheld Computers
Charging Docks and Cradles
Programmable Current Source
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
400mA Li-Ion Charger
V
IN
= 9V
MBRM120T3
Typical Li-Ion Charge Cycle
CONSTANT
CURRENT
CONSTANT
VOLTAGE
BATTERY VOLTAGE
400
300
CHARGE CURRENT
200
100
10µF
0
1731 TA01
CHARGE CURRENT (mA)
7
2k
CHARGE
STATUS
V
CC
SENSE
2
CHRG
DRV
8
6
R
SENSE
0.2Ω
Q1
Si9430DY
I
BAT
= 400mA
1µF
LTC1731-8.4
3
C
TIMER
0.1µF
TIMER
BAT
PROG
GND
4
1
5
R
PROG
*
19.6k
+
2-CELL
Li-ION
0
0.5
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
U
9
U
U
BATTERY VOLTAGE(V)
400mA HR BATTERY
8
CHRG
LED OFF
7
TIMER
STOPS
6
3.0
2.0
1.5
1.0
TIME (HOURS)
2.5
1731 TA01b
sn1731 17318fs
1
LITEON [ LITE-ON TECHNOLOGY CORPORATION ]
