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

LTC3900
Typical Application
0.47µF
0.1µF
36V to 72V Input to 12V at 20A “No Optocoupler” Synchronous “Bus Converter”
V_IN
36V TO 72V
V_U1
47k
82k
BCX55
PA0815.002
••
BAS516
L1
2.4µH
18V
12V
0.1µF
Si7370
PH4840
×2
×2
10k
V_OUT
12V, ±10%,
20A MAX
C_OUT
33µF, 16V
X5R, TDK
×3
370k
13.2k
115k
27k
7
SD_V_SEC
3
R_OSC
9
BLANK
5
SS_MAXDC
59k 10k
LT1952
6
V_R = 2.5V
1
COMP
2 _{FB = 1.23V}
OUT ¹⁴
15
V_IN
8
GND
13
PGND
12
DELAY
OC ¹¹
10
I_SENSE
SOUT ¹⁶
2.2µF, 100V
×2
•
PH21NQ15
×2
LTC3900
5 _FG
CG ³
6 _GND
CS^{+ 1}
10k
V_U1
1µF
4 _VCC
CS^{– 2}
10k
BAT
8V ^{8 SYNC TIMER 7}
760
1µF
39k
BIAS
R_T
15k
C_T
1nF
9mΩ
1nF
8V
470Ω
220pF
560Ω
BIAS
L1: PULSE PA1494.242
ALL CAPACITORS ARE TDK, X5R CERAMIC
Q4470-B
3900 TA07a
LTC3900-Based Synchronous “Bus Converter” Efficiency vs Load Current
96.0
16
95.5
EFFICIENCY
95.0
12
94.5
94.0
8
POWER LOSS
93.5
V_IN = 48V
V_OUT = 12V
93.0
4
4 6 8 10 12 14 16 18 20
LOAD CURRENT (A)
3900 TA07b
Related Parts
PART NUMBER DESCRIPTION
COMMENTS
LT1952/LT1952-1 Synchronous Forward Converter Controllers
Ideal for Medium Power 24V or 48V Input Isolated Applications
LTC3901
Secondary Side Synchronous Driver for Push-Pull and Full Similar to the LTC3900, Used in Full Bridge and Push-Pull
Bridge Converters
Converters
LT4430
Secondary Side Optocoupler Driver
Optocoupler Driver with Precise Reference Voltage
LT1431
Programmable Reference
Adjustable Shunt Voltage Regulator with 100mA Sink Capability
LTC3726/LTC3725 Synchronous No Opto Forward Converter Controller Chip Set Ideal for Medium Power 24V or 48V Input Isolated Applications
LTC3723-1/
LTC3723-2
Synchronous Push-Pull Controllers
High Efficiency with On-Chip MOSFET Drivers
LTC3721-1/
LTC3721-2
Nonsynchronous Push-Pull Controllers
Minimizes External Components, On-Chip MOSFET Drivers
LTC3722/
LTC3722-2
Synchronous Phase Modulated Full Bridge Controllers
Ideal for High Power 24V or 48V Input Applications
3900fb
20 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ^● FAX: [phone] ^● www.linear.com
LT 0511 REV B • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2003