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LTC1731-8.2/LTC1731-8.4

sn1731 17318fs

FEATURES

APPLICATIO S

DESCRIPTIO

TYPICAL APPLICATIO

Lithium-Ion Linear

Battery Charger Controller

The LTC

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 15

µA. 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.

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Complete Linear Charger Controller for

2-Cell Lithium-Ion Batteries

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1% Voltage Accuracy

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Programmable Charge Current

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C/10 Charge Current Detection Output

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Programmable Charge Termination Timer

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Space Saving 8-Pin MSOP Package

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Automatic Sleep Mode When Input Supply

is Removed (15

µA Battery Drain)

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Automatic Trickle Charging of Low Voltage Cells

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Programmable for Constant-Current-Only Mode

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Cellular Phones

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Handheld Computers

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Charging Docks and Cradles

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Programmable Current Source

, LTC and LT are registered trademarks of Linear Technology Corporation.

400mA Li-Ion Charger

SENSE

DRV

2k

0.2

Ω

19.6k

2-CELL

Li-ION

LTC1731-8.4

*SHUTDOWN INVOKED BY FLOATING THE PROG PIN

BAT

CHRG

8

7

MBRM120T3

10

µF

1731 TA01

1

µF

0.1

µF

Q1

Si9430DY

6

1

5

4

2

3

TIMER

PROG

GND

+

CHARGE

STATUS

Typical Li-Ion Charge Cycle

TIME (HOURS)

0

400

300

200

100

0

9

8

7

6

1.5

2.5

1731 TA01b

0.5

1.0

2.0

3.0

CONSTANT

VOLTAGE

CONSTANT

CURRENT

TIMER

STOPS

CHRG

LED OFF

BATTERY VOLTAGE

400mA HR BATTERY

CHARGE CURRENT