LTC3900_1 Datasheet, PDF (13/20 Pages) Linear Technology – Synchronous Rectifier Driver for Forward Converters

LTC3900
typical applications
36V to 72V Input to 12V and 24V (or ± 12V), 2A Output Converter in 1/8th Brick Footprint
V_IN
36V TO 72V
2.2µF
V_U1
82k BCX56
7
1.5mH
PDZ10B
2_•
BAS516
1
9
0.1µF
F_G
V_IN
3_•
10k
L1: DRQ127-220
L1A
Q2
0.1µF
C_G
BAS516
10k
Q3
BAS516
V_OUT2
24V
2A
150µF
16V
4
V_FB
22k
BC857BF
1.2k
33k
115k
LT1952-1
1 _COMP
2 _{FB = 1.23V}
3 _ROSC
S_OUT ¹⁶
V_IN ¹⁵
OUT ¹⁴
S_OUT
Si7462
V_U1
1µF
8
10
T1
PA1577
F_G
0.1µF
4 _SYNC
5 _MAXDC
PGND ¹³
DELAY ¹²
100pF
0.030R
6 _{VR = 2.5V}
7 _SD
OC ¹¹
I_SENSE ¹⁰
145k
680Ω
10k
13.3k
8 _GND
BLANK ⁹
10k
82k
0.47µF
340k
V_AUX
CG
V_OUT1
V_IN
22k
56k
1k
BCX55
Q2, Q3, Q4, Q5 = Si7850
PDZ7.5B
Q4
47k
C_G
LTC3900
1 _CS+
8
SYNC
2 _CS–
7
TIMER
3
CG
6
GND
4
V_CC
5
FG
FG
38.3k
1µF
L1B
Q5
V_OUT1
12V
2A
33µF
16V
470pF
560R
220pF
S_OUT
•
PE-68386
V_U1
V_FB
PS2801-1
470R
BAS516
V_AUX
LT4430
1
6
V_CC
2
OPTO
5 ^3.92k
GND COMP
3
OC
4
FB
15nF
100k
1µF
5.23k
33pF
V_OUT1
3900 TA02
The LTC3900 can drive multiple synchronous output
rectifiers. The 12V and 24V or ±12V output converter
has good cross regulation due to low voltage drops in
the output MOSFETs. Other combinations like 3.3V and
–5V or 1.5V and 5V can be easily achieved by changing
the transformer turns ratio.
3900fb
13