LTC1731ES8-84 Datasheet, PDF (1/12 Pages) Linear Technology – Lithium-Ion Linear Battery Charger Controller

LTC1731-8.2/LTC1731-8.4
Lithium-Ion Linear
Battery Charger Controller
FEATURES
s _{Complete Linear Charger Controller for}
2-Cell Lithium-Ion Batteries
s _{1% Voltage Accuracy}
s _{Programmable Charge Current}
s _{C/10 Charge Current Detection Output}
s _{Programmable Charge Termination Timer}
s _{Space Saving 8-Pin MSOP Package}
s _{Automatic Sleep Mode When Input Supply}
is Removed (15µA Battery Drain)
s _{Automatic Trickle Charging of Low Voltage Cells}
s _{Programmable for Constant-Current-Only Mode}
U
APPLICATIO S
s _{Cellular Phones}
s _{Handheld Computers}
s _{Charging Docks and Cradles}
s _{Programmable Current Source}
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTIO
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.
TYPICAL APPLICATIO
400mA Li-Ion Charger
V_IN = 9V
MBRM120T3
CHARGE
STATUS
C_TIMER
0.1µF
7
2k
V_CC
8
SENSE
2
CHRG
DRV ⁶
LTC1731-8.4
3
TIMER
1
BAT
5
PROG
GND
4
R_PROG*
19.6k
R_SENSE
0.2Ω
Q1
Si9430DY
I_BAT = 400mA
+
2-CELL
Li-ION
1µF
10µF
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
1731 TA01
Typical Li-Ion Charge Cycle
CONSTANT
CONSTANT
9
CURRENT
VOLTAGE
BATTERY VOLTAGE
400
8
400mA HR BATTERY
300
CHARGE CURRENT
200
7
CHRG
LED OFF _TIMER
100
STOPS
0
6
0 0.5 1.0 1.5 2.0 2.5 3.0
TIME (HOURS)
1731 TA01b
sn1731 17318fs
1