Datasheet

12
LT1170/LT1171/LT1172
Positive-to-Negative Buck-Boost Converter
High Efficiency Constant Current Charger
Backlight CCFL Supply (see AN45 for details)
C4
1µF
V
IN
10V TO
30V
1170/1/2 TA10
R3
5k
C5
100µF*
D3
†
1N4001
C2
0.1
µF
V
IN
V
C
FB
V
SW
LT1170
GND
V
OUT
–12V
2A
REQUIRED IF INPUT LEADS ≥ 2"
PULSE ENGINEERING 92114, COILTRONICS 50-2-52
*
**
R2
1.24k
L1**
50µH
R5
†
470Ω, 1W
TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES
BELOW 10V, CONNECT ANODE OF D3 TO V
IN
, AND
REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT
CURRENTS. C1 ≈ (500µF)(I
OUT
).
FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO
0.3µF, AND REDUCE R6 TO 100Ω.
†
C3
2µF
D2
1N914
R4
47Ω
C1
†
1000µF
D1
R6
470
Ω
R1
10.7k
+
+
+ +
D2
MBR340
1170/1/2 TA11
INPUT VOLTAGE
> V
BAT
+ 2V < 35V
C2
2.2µF
35V
TANTALUM
R7
22k
R8
1k
C3
0.47µF
V
+
V
–
R4
1k
C4
200µF
25V
BATTERY
2V TO 25V
L2*
10µH, 1A
L1
100µH, 1A
R5
0.05Ω
R3
25k
R2
1k
RUN = 0V
SHUTDOWN = 5V
* L2 REDUCES RIPPLE CURRENT INTO
THE BATTERY BY ABOUT 20:1.
IT MAY BE OMITTED IF DESIRED.
I =
1.244V • R4
R3 • R5
= 1A AS SHOWN
CHRG
R6
78k
V
IN
C
V
FB
V
SW
GND
D1
1N5819
C4
0.01µF
LT1006
+
–
+
LT1171
C1
200µF
35V
1A
2N3904
+ +
+
+
GND
2µF
1170/1/2 TA12
D1
1N914
33pF
3kV
10µF
TANT
R3
10k
50k
INTENSITY
ADJUST
1N5818
L1**
300µH
INPUT VOLTAGE
†
4.5V TO 20V
Q1,Q2 = BCP56 OR MPS650/561
COILTRONICS CTX300-4
SUMIDA 6345-020 OR COILTRONICS 110092-1
A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
*
**
***
†
C6
1 F
µ
R1
560Ω
1k
LT1172
IN
V
V
C
V
SW
E2
E1
D2
1N914
LAMP
FB
L2***
0.02µF
A
B
Q1*
Q2*
+
+
TYPICAL APPLICATIO S
U