LT1072CN8 Datasheet, PDF (10/16 Pages) Linear Technology – 1.25A High Efficiency Switching Regulator

LT1072
TYPICAL APPLICATIO S
Flyback Converter
V_IN
20 TO 30V
C4 ⁺
25µF*
L2
10µH
C4
200µF
OPTIONAL
V_IN
FILTER
0V
D1
V_OUT
5V
** ^R4
1k
C3
1 N*
0.47µF
+
N* = ¹
3
C1
500µF
1.5A
0V
D2
V_IN
V_SW
R1
3.74k
0
LT1072
0
GND
V_C ^FB
R3
C2 ^1.5k
0.15µF
*REQUIRED IF INPUT LEADS ≥ 2"
**OPTIONAL TO REPLACE R4 AND C3
R2
0
1.24k
0
V_SNUB
CLAMP TURN-ON
SPIKE
a
b
PRIMARY FLYBACK VOLTAGE = ^{VOUT + Vf}
LT1072 SWITCH VOLTAGE
N
AREA “a” = AREA “b” TO MAINTAIN
V_OUT + V_f ZERO DC VOLTS ACROSS PRIMARY
c
d
∆I
N • V_IN SECONDARY VOLTAGE
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
I_PRI
PRIMARY CURRENT
I_PRI
N
SECONDARY CURRENT
I_PRI
LT1070 SWITCH CURRENT
I_PRI
SNUBBER DIODE CURRENT
t = ^{(IPRI) (LL)}
V_SNUB
LT1072 • TA04
Negative to Positive Buck-Boost Converter
C4 ⁺
25µF*
OPTIONAL
INPUT
FILTER
L3
V_IN
–12V
L2
L1**
220µH
OPTIONAL
C3
OUTPUT
FILTER
V_IN
V_SW
LT1072
GND
V_C ^FB
R3
2.2k
C1
0.22µF
D1
C2 ⁺
1000µF
V_OUT
12V, 0.5A
R1
11.3k
Q1
R2
1.24k
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 52626
LT1072 • TA05
External Current Limit
+
– ^VIN
Q1
V_IN
V_SW
LT1072
GND
V_C ^FB
R1
1k
C1
1000pF
R_S
R2
C2
NOTE THAT THE LT1072 GND PIN
IS NO LONGER COMMON TO V_IN (–)
LT1072 • TA06
1072fc
10