LT1170 Datasheet, PDF (11/20 Pages) Linear Technology – 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators

LT1170/LT1171/LT1172
TYPICAL APPLICATIO S (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
Driving High Voltage FET
(for Off-Line Applications, See AN25)
+
10V TO
20V
V_IN
V_SW
LT1170
G
D
Q1
D1
GND
1170/1/2 TA05
Negative-to-Positive Buck-Boost Converter^†
External Current Limit
V_X
R2
R1
500Ω
≈ 2V
D1
LT1170
GND
V_C
1170/1/2 TA06
External Current Limit
L1**
50µH
L2
OPTIONAL
C3
OUTPUT
FILTER
+
C4*
100µF
OPTIONAL
INPUT FILTER
L3
V_IN
V_SW
LT1170
FB
GND
V_C
R3
2.2k
D1
+
C2
1000µF
V_OUT
12V
R1 ^2A
11.3k
Q1
R2
1.24k
V_IN
–20V
C1
0.22µF
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114, COILTRONICS 50-2-52
† _{THIS CIRCUIT IS OFTEN USED TO CONVERT –48V TO 5V. TO GUARANTEE}
FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN
IN AN19, FIGURE 39, SHOULD BE ADDED WITH C1 REDUCED TO 200pF.
1170/1/2 TA07
Negative Buck Converter
V_IN
V_SW
+
– ^VIN
LT1170
FB
GND
V_C
R1
1k
Q1
C1
1000pF
R_S
NOTE THAT THE LT1170
GND PIN IS NO LONGER
COMMON TO V_IN–.
R2
C2
1170/1/2 TA08
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
+
C3*
100µF
OPTIONAL
INPUT FILTER
L3
V_IN
–20V
V_IN
V_SW
LT1170
FB
GND
V_C
C1
R3
+
D1
L1**
50µH
C2
1000µF
R1
4.64k
R4
Q1
12k
2N3906
LOAD
–5.2V
4.5A
R2
1.24k
OPTIONAL ₊
OUTPUT
FILTER
C4
200µF
L2
4µH
1170/1/2 TA09
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