LT1513/LT1513-2
SEPIC Constant- or
Programmable-Current/
Constant-Voltage Battery Charger
FEATURES
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DESCRIPTION
The LT
®
1513 is a 500kHz current mode switching regula-
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Charger Input Voltage May Be Higher, Equal to or
Lower Than Battery Voltage
Charges Any Number of Cells Up to 20V
1% Voltage Accuracy for Rechargeable Lithium
Batteries
100mV Current Sense Voltage for High Efficiency
(LT1513)
0mV Current Sense Voltage for Easy Current
Programming (LT1513-2)
Battery Can Be Directly Grounded
500kHz Switching Frequency Minimizes
Inductor Size
Charging Current Easily Programmable or Shut Down
APPLICATIONS
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Charging of NiCd, NiMH, Lead-Acid or Lithium
Rechargeable Cells
Precision Current Limited Power Supply
Constant-Voltage/Constant-Current Supply
Transducer Excitation
Universal Input CCFL Driver
TYPICAL APPLICATION
WALL
ADAPTER
INPUT
•
L1A*
C2**
4.7µF
V
SW
5
L1B*
V
FB
V
C
TAB
1
R5
270Ω
C5
0.1µF
I
FB
3
2
R4
39Ω
C4
0.22µF
R3
0.08Ω
LT1513 • TA01
2.4
+
C3
22µF
25V
7
V
IN
LT1513
6
S/S
GND
4
D1
†
1.25A
CURRENT (A)
2.2
2.0
1.8
CHARGE
SYNC
AND/OR
SHUTDOWN SHUTDOWN
R1
•
R2
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0
5
+
C1
22µF
25V
×
2
* L1A, L1B ARE TWO 10µH WINDINGS ON A
COMMON CORE: COILTRONICS CTX10-4
** CERAMIC MARCON THCR40EIE475Z OR TOKIN 1E475ZY5U-C304
†
MBRD340 OR MBRS340T3. MBRD340 HAS 5µA TYPICAL
LEAKAGE, MBRS340T3 50µA TYPICAL
Figure 1. SEPIC Charger with 1.25A Output Current
INDUCTOR = 10µH
ACTUAL PROGRAMMED CHARGING CURRENT WILL BE
INDEPENDENT OF INPUT VOLTAGE IF IT DOES NOT
EXCEED VALUES SHOWN
LT1513 • TA02
U
U
U
Maximum Charging Current
SINGLE Li-Ion CELL
(4.1V)
DOUBLE Li-Ion
CELL (8.2V)
12V
16V
20V
BATTERY
VOLTAGE
10
20
15
INPUT VOLTAGE (V)
25
30
1
LINER [ LINEAR TECHNOLOGY ]
