LTC3725 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC3725' PDF : 20 Pages View PDF
FEATURES
■ High Speed Gate Driver for Forward Converter
■ On-Chip Rectifier and Self-Starting Architecture
Eliminates Need for Separate Gate Drive Bias
Supply
■ Wide Input Voltage Supply Range: 9V and Up
■ Linear Regulator Controller for Fast Start-Up
■ Precision UVLO with Adjustable Hysteresis
■ Overcurrent Protection
■ Volt-Second Limit Prevents Transformer Core
Saturation
■ Voltage Feedforward for Fast Transient Response
■ Available in 10-Lead MSOP Package
U
APPLICATIO S
■ Isolated 48V Telecommunication Systems
■ Internet Servers and Routers
■ Distributed Power Step-Down Converters
■ 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
×2
VIN–
36V-72V to 3.3V/30A Isolated Single-Switch Forward Converter
T1
•
•
L1
0.85µH
Si7450DP
0.030Ω
1W
•
2.2nF
200V
HAT2165
×2
0.0012Ω
1W
HAT2165
×2
B0540W
1.2Ω
1/4W
100µF
6.3V
×2
10µF
365k
15k
100k
FDC2512
NDRV GATE IS
VCC
FB/IN+
UVLO LTC3725
1µF
SSFLT
FS/IN–
VSLMT PGND GND
33nF
0.1µF
T2
••
5.1k
162k
L1: PULSE PA1294.910
T1: PULSE PA0815
T2: PULSE PA0297
FCX491A
2.2µF
1µF
FG SW IS–
IS+
PT+
SG VIN NDRV VCC MODE
LTC3706
FB
PT–
GND PGND RUN/SS SLP REGSD FS/SYNC PHASE ITH
33nF
100k
470pF
3.3k
47nF
VOUT+
3.3V
30A
+
220µF
6.3V
VOUT–
2.74k
604Ω
3725 TA01
3725f
1
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