Datasheet

17
LT1776
TYPICAL APPLICATIONS
U
(a)
V
IN
C1
NC
Q1
PN2484
Q2*
2N2369
1776 F07a
V
+
V
–
IN
–
IN
+
U2
LTC1440
REF
HYST
OUT
4
7
12
3
6
5
8
GND
+
C2
+
D1
R1
39k
5%
V
OUT
5V
R2
10k
5%
R5
22k
R6
2.4M
L1
R3
323k
1%
R4
100k
1%
C3
100pF
R7
10M
C1: PANASONIC HFQ 39µF AT 63V
C2: AVX D CASE 100µF 10V
TPSD107M010R0080
D1: MOTOROLA 100V, 1A,
SMD SCHOTTKY
MBRS1100 (T3)
L1: COILCRAFT DO3316-104
*ANY NPN WITH EMITTER-BASE
BREAKDOWN OF <7V CAN BE USED
V
IN
V
CC
V
SW
U1
LT1776
FB
V
C
SHDN
SYNC
2
5
4
3
7
8
6
1
GND
Figure 7. Burst Mode Operation Configuration for High Efficiency at Light Load
(b)
LOAD CURRENT (mA)
1
60
EFFICIENCY (%)
70
80
90
10 100 1000
1776 F07b
50
40
30
20
V
IN
= 10V
V
IN
= 30V
V
IN
= 40V
V
IN
= 20V