LT1513/LT1513-2
SEPIC Constant- or
Programmable-Current/
Constant-Voltage Battery Charger
U
DESCRIPTION
FEATURES
The LT®1513 is a 500kHz current mode switching regula-
tor specially configured to create a constant- or program-
mable-current/constant-voltagebatterycharger.Inaddition
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
currentsensecircuittobegroundreferredandcompletely
separatedfromthebatteryitself,simplifyingbatteryswitch-
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.
■
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 CurrenUt Easily Programmable or Shut Down
APPLICATIONS
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.
■
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
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
U
TYPICAL APPLICATION
Maximum Charging Current
L1A*
WALL
ADAPTER
INPUT
•
2.4
C2**
7
C3
22µF
25V
+
†
4.7µF
2.2
D1
SINGLE Li-Ion CELL
5
2
V
IN
(4.1V)
V
SW
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
1.25A
CHARGE
DOUBLE Li-Ion
CELL (8.2V)
L1B*
LT1513
R1
R2
SYNC
6
•
S/S
GND
V
FB
AND/OR
C1
SHUTDOWN
SHUTDOWN
V
C
I
+
FB
12V
R4
39Ω
22µF
25V
× 2
1
3
4
TAB
16V
R5
270Ω
20V
C4
R3
C5
0.1µF
0.22µF
0.08Ω
BATTERY
VOLTAGE
LT1513 • TA01
*
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
0
5
10
15
20
25
30
INPUT VOLTAGE (V)
**
†
INDUCTOR = 10µH
ACTUAL PROGRAMMED CHARGING CURRENT WILL BE
INDEPENDENT OF INPUT VOLTAGE IF IT DOES NOT
EXCEED VALUES SHOWN
LT1513 • TA02
Figure 1. SEPIC Charger with 1.25A Output Current
1