LTC3725

1

3725f

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

■

Internet Servers and Routers

■

On-Chip Rectifier and Self-Starting Architecture

Eliminates Need for Separate Gate Drive Bias

Supply

■

Wide Input Voltage Supply Range: 9V and Up

■

Overcurrent Protection

Saturation

■

Voltage Feedforward for Fast Transient Response

Single-Switch Forward

Controller and Gate Driver

The LTC

converter and includes an on-chip gate driver.

For secondary-side control, combine the LTC3725 with

the LTC3706 PolyPhase

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.

36V-72V to 3.3V/30A Isolated Single-Switch Forward Converter

, 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

1

µF

100V

×2

+

36V TO 72V

–

2.2nF

200V

10

µF

100

µF

6.3V

×2

220

µF

6.3V

+

3.3V

30A

–

47nF

470pF

33nF

B0540W

Si7450DP

33nF

15k

1

µF

0.1

µF

0.030

Ω

1W

1

µF

2.2

µF

0.0012

Ω

1W

HAT2165

×2

HAT2165

×2

L1

0.85

µH

T2

•

•

162k

L1: PULSE PA1294.910

T1: PULSE PA0815

T2: PULSE PA0297

5.1k

3.3k

100k

2.74k

604

Ω

3725 TA01

1.2

Ω

1/4W

100k

UVLO

SSFLT

GATE

LTC3725

NDRV

GND

PGND

365k

FDC2512

T1

•

•

FG SW

–

NDRV

GND PGND RUN/SS SLP REGSD FS/SYNC

PHASE

FCX491A

FB

LTC3706

+

•