1

LT1513/LT1513-2

SEPIC Constant- or

Programmable-Current/

Constant-Voltage Battery Charger

The LT

tor specially configured to create a constant- or program-

mable-current/constant-voltage battery charger. In addition

to the usual voltage feedback node, it has a current sense

feedback circuit for accurately controlling output current

of a flyback or SEPIC (Single-Ended Primary Inductance

Converter) topology charger. These topologies allow the

current sense circuit to be ground referred and completely

separated from the battery itself, simplifying battery switch-

ing and system grounding problems. In addition, these

topologies allow charging even when the input voltage is

lower than the battery voltage. The LT1513 can also drive

a CCFL Royer converter with high efficiency in floating or

grounded mode.

Maximum switch current on the LT1513 is 3A. This allows

battery charging currents up to 2A for a single lithium-ion

cell. Accuracy of 1% in constant-voltage mode is perfect

for lithium battery applications. Charging current can be

easily programmed for all battery types.

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Charger Input Voltage May Be Higher, Equal to or

Lower Than Battery Voltage

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Charges Any Number of Cells Up to 20V

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1% Voltage Accuracy for Rechargeable Lithium

Batteries

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100mV Current Sense Voltage for High Efficiency

(LT1513)

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0mV Current Sense Voltage for Easy Current

Programming (LT1513-2)

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Battery Can Be Directly Grounded

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500kHz Switching Frequency Minimizes

Inductor Size

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Charging Current Easily Programmable or Shut Down

FEATURES

INPUT VOLTAGE (V)

05

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

25

LT1513 • TA02

10

15

20

30

12V

INDUCTOR = 10

µH

ACTUAL PROGRAMMED CHARGING CURRENT WILL BE

INDEPENDENT OF INPUT VOLTAGE IF IT DOES NOT

EXCEED VALUES SHOWN

SINGLE Li-Ion CELL

(4.1V)

DOUBLE Li-Ion

CELL (8.2V)

16V

20V

BATTERY

VOLTAGE

Maximum Charging Current

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

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Charging of NiCd, NiMH, Lead-Acid or Lithium

Rechargeable Cells

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Precision Current Limited Power Supply

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Constant-Voltage/Constant-Current Supply

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Transducer Excitation

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Universal Input CCFL Driver

Figure 1. SEPIC Charger with 1.25A Output Current

LT1513

L1A*

L1B*

1.25A

13

2

5

7

•

•

6

TAB

4

GND

LT1513 • TA01

SYNC

AND/OR

SHUTDOWN

WALL

ADAPTER

INPUT

S/S

C3

22

µF

25V

C2**

4.7

µF

C5

0.1

µF

*

**

†

L1A, L1B ARE TWO 10

µH WINDINGS ON A

COMMON CORE: COILTRONICS CTX10-4

CERAMIC MARCON THCR40EIE475Z OR TOKIN 1E475ZY5U-C304

MBRD340 OR MBRS340T3. MBRD340 HAS 5

µA TYPICAL

LEAKAGE, MBRS340T3 50

µA TYPICAL

C4

0.22

µF

R4

39

Ω

R1

R2

R5

270

Ω

R3

0.08

Ω

C1

22

µF

25V

× 2

CHARGE

SHUTDOWN

+

+