Datasheet

LTC3805-5
17
38055fe
TYPICAL APPLICATIONS
Figure 9. Isolated Telecom Supply: 18V to 72V Input to 3.3V/3A Output
Efficiency and Power Loss vs Load Current and V
IN
LOAD CURRENT (A)
0.01
60
EFFICIENCY (%)
POWER LOSS (W)
80
100
0.1 1 10
38055 TA03b
40
50
70
90
30
20
2.0
3.0
4.0
1.0
1.5
2.5
3.5
0.5
0
18V
36V
48V
60V
72V
EFFICIENCY
POWER LOSS
V
IN
OC
COMP
FB
GND
OPTO
75k15.8k
1µF
0.47µF
100k
47pF
22.1k
2200pF
250VAC
274Ω
2.2nF
221k
BAS516
BAS516
D2
BAS516
FDC2512
V
IN
V
CC
V
CC
11
5
4
3
2
1
6
7
8
2
3
4
PA1277NL
1
7
6
5
8
D1
PDS1040
100µF
6.3V
100µF
6.3V
100µF
6.3V
9
1
3
2
6
4
5
10
R
BIAS
402Ω
10W
BAS516 BA760
68Ω
150pF
200V
PDZ6.8B
6.8V
MMBTA42
V
IN
–
6.8k
221k
U1
LTC3805-5
I
TH
GND
SSFLT
RUN
GATE
OC
I
SENSE
SYNCFS
FB
V
CC
56k
38055 F09
0.04Ω
V
OUT
+
3.3V
3A
V
OUT
–
PS2801-1-K
U2
LT4430
V
IN
+
18V TO
72V
2.2µF
100V
2.2µF
100V
0.022µF
1µF
221k
3.01k