LT1513-2 Linear Technology, LT1513-2 Datasheet - Page 13

• Manufacturer Part Number: LT1513-2
• Description: SEPIC Constant- or Programmable-Current/ Constant-Voltage Battery Charger
• Manufacturer: Linear Technology

TYPICAL APPLICATIONS
Lithium-Ion Battery Charger with
Switchable Charge Current
Many battery chemistries require several constant-current
settings during the charging cycle. The circuit shown in
Figure 8 uses the LT1513-2 to provide switchable 1.35A and
0.13A constant-current modes. The circuit is based on a
standard SEPIC battery charger circuit set to a single
lithium-ion cell charge voltage of 4.1V. The LT1513-2 has I
referenced to ground allowing a simple resistor network to
set the charging current values. In constant-current mode,
the I
current, until I
FB
error amplifier drives the FB pin, increasing charging
R4
is balanced by I
SHUTDOWN
PRECHARGE
CHARGE
CHARGE
V
IN
3.3V
Q1
R6
10k
R7
910
R5
.
+
U
C3
25 F
25V
R3
330
C5
0.1 F
Figure 8. Lithium-Ion Battery Charger
7
6
1
V
S/S
V
IN
C
•
LT1513-2
CTX10-4
GND
L1A
4
FB
V
36k
V
R5
SW
I
FB
FB
There are several ways to control I
resistor network as shown here. If the lithium cell requires
precharging, Q1 is turned on, setting a constant current of
0.13A. When charge voltage is reached, Q1 is turned off,
programming the full charge current of 1.35A. As the cell
voltage approaches 4.1V, the voltage sensing network (R1,
R2) starts driving the V
constant-voltage mode. As charging current falls, the output
remains in constant-voltage mode for the remainder of the
charging cycle. When charging is complete, the LT1513-2
can be shut down with the S/S pin.
5
2
3
I
CHARGE
C4
0.22 F
4.7 F
C2
4.7k
R4
•
MBRS330T3
R3
0.25
L1B
(
D1
I
R
5
)(
R
R1
78.7k
0.5%
R2
34k
0.5%
4
R
) –
FB
3
+
I
pin, changing the LT1513-2 to
FBVOS
LT1513/LT1513-2
1513 F08
C1
22 F
25V
Li-Ion
RECHARGABLE
CELL
GND
2
R5
including DAC, PWM or
13