Datasheet

20
LTC1698
1698f
Figure 12. LT3781/LTC1698 36V
IN
-72V
IN
to 3.3V/15A Isolated Synchronous Forward Converter-Quarter Brick
TYPICAL APPLICATIO S
U
V
CC
13
2 1
5
1µF
0.01µF
82pF
OVLO SHDN
1.24k 1%
10k
270k
1/4W
100µF
20V
1000pF
5V
REF
6
F
SET
4700pF
8
SS
10
BAT54
BAT54
PULSE ENG
PA0184
BAS21
BAS21
BAT54
ZETEX ZVN3310F
9
V
C
PGND
12
V
FB
37 4
THERM
LT3781
SYNC SGND
52.3k
1%
10Ω
1k
3k
1k
1k
2k
FZT690B
4.7µF
0.22µF
1
10k
5V
REF
MOC207
7
143
8 1
5 4
5
14
15
6 5
8
2
3300pF
4700pF
220pF
5V
REF
14
SG
+
11
SENSEBG
18
BSTREF
19 1617
TG NC NC
15 20
BAS21
0.1µF
1mH
DO1608C-105
COILCRAFT
V
BST
3.3µH
D01608C-332
COILCRAFT
0.022µF
1000pF
••
SYNC V
FB
OVPIN
MARGIN
I
COMP
V
DD
OPTODRV
V
AUX
0.1µF
1612 11
FG
2
CG
PGND GND
LTC1698
PWRGD
6
8 9 7 13
1.78k 1%
1.24k 1%
3.01k 1%
2.43k 1%
3410
V
COMP
1698 F12
1k
0.22µF
MBR0540
0.03Ω
Si7456DP
Si7456DP
1000pF
100V
1000pF 100V
2200pF
250V
MURS120
MURS120
10Ω
•
••
T1
38431
SCHOTT
10Ω
MMBT3906
MMBD914
MMBT3906
V
IN
+
V
IN
–
0.82µF 100V
0.82µF 100V ×2
V
OUT
+
V
OUT
–
330pF
+
+
+
330µF
6.3V KEMET T520
330µF
6.3V KEMET T520
330µF
6.3V
KEMET
T520
330µF
6.3V
KEMET
T520
+
3.3Ω
V
CC
V
IN
V
CC
V
CC
10k
2.43k 1%
RT1
100k
0.1µF
ON/OFF
TRIM
V
OUT
+
4.7Ω
10V MMBZ5240B
470Ω
–
+
3.01k
1%
3.01k 1%
3.01k
1%
3.01k 1%
100Ω 1/4W
100Ω 1/4W
9V
V
OUT
V
OUT
+
3
4
2
1
LT1783CS5
+SENSE
–SENSE
OPTIONAL DIFFERENTIAL SENSE**
V
CC
V
IN
5V
REF
FQT7N10L
100Ω
1/4W
100Ω
1/4W
47k
62k 1/4W
4.7µF
MMBT3904
OPTIONAL FAST START*
V
IN
18V
MMBZ5248B
•
0.1µF
100Ω
9V
5
I
SNS
I
SNSGND
0.1µF
1k
1k
Si7892DP
Si7892DP Si7892DP Si7892DP
10Ω 1/4W
10Ω
1/4W
R
OUT
(OPTIONAL)
73.2k 1%
3300pF
R
IN
(OPTIONAL)
1 2 3 4
5 6
78