1

LTC3726

3726fb

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

OPTI-LOOP is a registered trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents, including 6144194. Other patents pending.

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

Secondary-Side Synchronous

Forward Controller

■

Secondary-Side Control for Fast Transient Response

■

Self-Starting Architecture Eliminates Need for

Separate Bias Regulator

■

Proprietary Gate Drive Encoding Scheme Reduces

System Complexity

■

Current Mode Control Ensures Current Sharing

■

PLL Fixed Frequency: 100kHz to 500kHz

■

±1% Output Voltage Accuracy

■

OPTI-LOOP Compensation

■

Available in a Narrow 16-Lead SSOP Package

■

Isolated 48V Telecommunication Systems

■

Internet Servers and Routers

■

Distributed Power Step-Down Converters

■

Automotive and Heavy Equipment

36V-72V to 3.3V/20A Isolated Forward Converter

The LTC

nous forward converters. When used in conjunction with

the LTC3705/LTC3725 gate driver and primary-side con-

trollers, the part creates a complete isolated power supply

that combines the simplicity of OPTI-LOOP

tion with the speed of secondary-side control.

The LTC3726 has been designed to simplify the design of

highly efficient, secondary-side forward converters. Work-

ing in concert with the LTC3705 or LTC 3725, the LTC3726

forms a robust, self-starting converter that eliminates the

need for the separate bias regulator that is commonly used

in secondary-side control applications. In addition, a pro-

prietary scheme is used to multiplex gate drive signals and

DC bias power across the isolation barrier through a

single, tiny pulse transformer.

The LTC3726 is available in a 16-lead SSOP package.

NDRV

GND

PGND VSLMT

UVLO

BOOST

LTC3705

BAS21

FQT7N10

0.22

µF

10

µF

25V

CMPSH1-4

1.2

Ω

L1

1.2

µH

TG

TS BG IS

T2

1

µF

162k

L1: COILCRAFT SER2010-122

T1: PULSE PA0807

T2: PULSE PA0297

33nF

30m

Ω

1W

2m

Ω

2W

Si7336ADP

Si7336ADP

×2

T1

•

•

MURS120

Si7852DP

Si7852DP

MURS120

33nF

15k

1%

365k

1%

100k

2.2

µF

25V

SS/FLT

–

+

330

µF

6.3V

×3

680pF

22.6k

1%

20k

102k

1%

–

3726 TA01

+

•

•

1

µF

100V

x3

FG

SW SG

GND

PGND

SLP

MODE

+

–

RUN/SS

LTC3726

ITH

FB/PHASE

FS/SYNC

7.5V

2.2

µF

FZT690B

5k