LTC3721-2 LINER [Linear Technology], LTC3721-2 Datasheet - Page 17

• Manufacturer Part Number: LTC3721-2
• Description: Synchronous Rectifier Driver for Forward Converters
• Manufacturer: LINER [Linear Technology]

Typical applicaTions
V
*CONVERTERS THAT USE THE LTC3900 CAN BE FORCED TO OPERATE IN DISCONTINUOUS CURRENT MODE
FB
AT LIGHT LOADS BY OFFSETTING THE CURRENT SENSE INPUT WITH R_DCM RESISTOR.
13.3k
BC857
0.1µF
442k
22k
V
IN
0.47µF
115k
33k
22.1k
36V TO 72V
1
2
3
4
5
6
7
8
The Discontinuous Current Mode (DCM) Operation of Circuit is About 10% More Efficient
COMP
FB = 1.23V
R
SYNC
MAXDC
V
SD
GND
R
OSC
with 1A-2A Loads. The No Load Input Current is 15mA in DCM Versus 90mA in CCM.
= 2.5V
V
2.2µF
IN
LT1952-1
158k
BLANK
DELAY
I
PGND
SENSE
S
OUT
OUT
V
82k
OC
IN
PZTA42
16
15
14
13
12
11
10
9
Synchronous Forward Converter With Pulse Skip Mode
PDZ10B
133k
910
S
82k
OUT
Si7430
1.5mH
V
U1
95
65
55
45
85
75
35
1µF
0
1.2k
V
0.015R
IN
1.5nF
V
FB
BAS516
5
V
U1
10
1
6
2
5
PA0369
• •
•
I
T1
OUT
15
PS2801-1
7
10
(A)
FG
CONTINUOUS
DISCONTINUOUS
CURRENT MODE
CURRENT MODE
20
1k
PDZ7.5B
V
V
IN
OUT
B0540W
10nF
0.22µF
B0540W
= 48V
25
BAS516
= 3.3V
3900 TA06b
270R
BCX55
CG
30
HA2165
2.2R
0.02µF
10k
10k
CG
10k
1µF
1
2
3
PA1671
1
2
3
4
1µF
V
GND
OC
CC
CS
CS
CG
V
LT4430
CC
100µF
R_DCM
LTC3900
+
–
3.3M
COMP
OPTO
TIMER
SYNC
FB
GND
*
FG
6
5
4
8
7
6
5
+
470µF
1.96k
18.2k
FG
V
AUX
V
3.3V
30A
OUT
38.3k
470pF
560R
15nF
47pF
82.5k
LTC3900
PE-68386
•
•
V
220pF
OUT
17
3900 TA06a
3900fb
S
OUT