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LTC3725 Datasheet, PDF (1/20 Pages) Linear Technology – Single-Switch Forward Controller and Gate Driver | |||
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FEATURES
â High Speed Gate Driver for Forward Converter
â On-Chip Rectifier and Self-Starting Architecture
Eliminates Need for Separate Gate Drive Bias
Supply
â Wide Input Voltage Supply Range: 9V and Up
â Linear Regulator Controller for Fast Start-Up
â Precision UVLO with Adjustable Hysteresis
â Overcurrent Protection
â Volt-Second Limit Prevents Transformer Core
Saturation
â Voltage Feedforward for Fast Transient Response
â Available in 10-Lead MSOP Package
U
APPLICATIO S
â Isolated 48V Telecommunication Systems
â Internet Servers and Routers
â Distributed Power Step-Down Converters
â Automotive and Heavy Equipment
LTC3725
Single-Switch Forward
Controller and Gate Driver
DESCRIPTIO
The LTC®3725 is a controller for a single-switch forward
converter and includes an on-chip gate driver.
For secondary-side control, combine the LTC3725 with
the LTC3706 PolyPhase® secondary-side synchronous
forward controller to create a complete forward converter
using a minimum of discrete parts. A proprietary scheme
is used to multiplex gate drive signals across the isolation
barrier through a tiny pulse transformer. The on-chip
rectifier and the same pulse transformer provide gate drive
bias power.
Alternatively, the LTC3725 can be used as a standalone
voltage mode controller in a primary-side control architec-
ture with optoisolator feedback. Voltage feedforward pro-
vides excellent line regulation and transient response.
, LTC and LT are registered trademarks of Linear Technology Corporation. PolyPhase is
a registered trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Patent Pending
TYPICAL APPLICATIO
VIN+
36V TO 72V
1µF
100V
Ã2
VINâ
36V-72V to 3.3V/30A Isolated Single-Switch Forward Converter
T1
â¢
â¢
L1
0.85µH
Si7450DP
0.030â¦
1W
â¢
2.2nF
200V
HAT2165
Ã2
0.0012â¦
1W
HAT2165
Ã2
B0540W
1.2â¦
1/4W
100µF
6.3V
Ã2
10µF
365k
15k
100k
FDC2512
NDRV GATE IS
VCC
FB/IN+
UVLO LTC3725
1µF
SSFLT
FS/INâ
VSLMT PGND GND
33nF
0.1µF
T2
â¢â¢
5.1k
162k
L1: PULSE PA1294.910
T1: PULSE PA0815
T2: PULSE PA0297
FCX491A
2.2µF
1µF
FG SW ISâ
IS+
PT+
SG VIN NDRV VCC MODE
LTC3706
FB
PTâ
GND PGND RUN/SS SLP REGSD FS/SYNC PHASE ITH
33nF
100k
470pF
3.3k
47nF
VOUT+
3.3V
30A
+
220µF
6.3V
VOUTâ
2.74k
604â¦
3725 TA01
3725f
1
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