Datasheet
LT1074/LT1076
13
sn1074 1074fds
Tapped-Inductor Buck Converter
Positive-to-Negative Converter with 5V Output
TYPICAL APPLICATIO S
U
+
+
V
SW
V
IN
V
C
GND
FB
LT1074HV
R1
2.8k
R2
2.21k
D2
35V
5W
C3
200
µ
F
50V
R3
1k
C2
0.2
µ
F
L1*
LT1074 •TA02
D1**
D3
1N5819
31
C1
4400
µ
F
(2 EA
2200
µ
F,
16V)
L2
5
µ
H
C4
390
µ
F
16V
0.01
µ
F
+
PULSE ENGINEERING #PE±65282*
**
†
MOTOROLA MBR2030CTL
IF INPUT VOLTAGE IS BELOW 20V,
MAXIMUM OUTPUT CURRENT WILL BE REDUCED. SEE AN44
V
IN
20V
†
TO 35V
V
OUT
5V, 10A
†
R3*
2.74k
V
IN
V
SW
V
GND
R4
1.82k*
C2
1000
µF
10V
L1
25
µH
5A
††
+
+
D1
†
MBR745
R1**
5.1k
V
C
C3
0.1
µF
C4**
0.01
µF
+
R2**
10k
C1
220
µF
50V
* = 1% FILM RESISTORS
D1 = MOTOROLA-MBR745
C1 = NICHICON-UPL1C221MRH6
C2 = NICHICON-UPL1A102MRH6
L1 = COILTRONICS-CTX25-5-52
V
4.5V to
40V
IN
–5V,1A***
+
200µF
10V
–
OPTIONAL FILTER
5
µH
LOWER REVERSE VOLTAGE RATING MAY BE USED FOR LOWER INPUT VOLTAGES.
LOWER CURRENT RATING IS ALLOWED FOR LOWER OUTPUT CURRENT. SEE AN44.
R1, R2, AND C4 ARE USED FOR LOOP FREQUENCY COMPENSATION WITH LOW INPUT VOLTAGE,
BUT R1 AND R2 MUST BE INCLUDED IN THE CALCULATION FOR OUTPUT VOLTAGE DIVIDER VALUES.
LOWER CURRENT RATING MAY BE USED FOR LOWER OUTPUT CURRENT. SEE AN44.
R3 = –2.37 (KΩ)
R1 = (R3) (1.86)
R2 = (R3) (3.65)
V
OUT
MAXIMUM OUTPUT CURRENT OF 1A IS DETERMINED BY MINIMUM INPUT
VOLTAGE OF 4.5V. HIGHER MINIMUM INPUT VOLTAGE WILL ALLOW MUCH HIGHER
OUTPUT CURRENTS. SEE AN44.
LT1074 • TA03
LT1074
FB
FOR HIGHER OUTPUT VOLTAGES, INCREASE R1, R2, AND R3 PROPORTIONATELY.
FOR INPUT VOLTAGE > 10V, R1, R2, AND C4 CAN BE ELIMINATED, AND COMPENSATION IS
DONE TOTALLY ON THE V PIN.
C
†
††
**
**