LTC3805-5_15 Datasheet, PDF (17/20 Pages) Linear Technology – Adjustable Frequency Current Mode Flyback/ Boost/SEPIC DC/DC Controller

TYPICAL APPLICATIONS
LTC3805-5
V_IN+
18V TO
72V
2.2µF
100V
V_IN–
2.2µF
100V
221k
221k
PDZ6.8B
6.8V
MMBTA42 _D2
BAS516
PA1277NL
4
5
6
7
3
8
2
150pF
200V _68Ω
R_BIAS
402Ω
1
D1
PDS1040
100µF
6.3V
FDC2512
0.04Ω
V_CC
BAS516 ^6.8k
10W
BAS516
274Ω
100µF
6.3V
100µF
6.3V
BAS516 BA760
V_OUT+
3.3V
3A
V_OUT–
100k
47pF
V_IN
221k
15.8k
0.022µF
V_CC
U1
1
2
3
4
5
LTC3805-5
SSFLT
I_TH
FB
RUN
FS GND
GATE
V_CC
OC
I_SENSE
SYNC
10
9
8
7
6
75k
11
1µF
3.01k
PS2801-1-K
2200pF
250VAC
1µF
0.47µF
U2
LT4430
1
2
V_IN
GND
3 _OC
OPTO ⁶
COMP ⁵
FB ⁴
2.2nF _56k
38055 F09
22.1k
Figure 9. Isolated Telecom Supply: 18V to 72V Input to 3.3V/3A Output
Efficiency and Power Loss vs Load Current and V_IN
100
4.0
18V
90
36V
3.5
48V
80
60V
72V
3.0
70
2.5
EFFICIENCY
60
2.0
50
1.5
40
1.0
30
20
0.01
0.5
POWER LOSS
0
0.1
1
10
LOAD CURRENT (A)
38055 TA03b
38055fe
17