LTC3726 Datasheet, PDF (1/16 Pages) Linear Technology – Secondary-Side Synchronous Forward Controller

LTC3726
Secondary-Side Synchronous
Forward Controller
FEATURES
■ _{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}
U
APPLICATIO S
■ _{Isolated 48V Telecommunication Systems}
■ _{Internet Servers and Routers}
■ _{Distributed Power Step-Down Converters}
■ _{Automotive and Heavy Equipment}
DESCRIPTIO
The LTC^®3726 is a secondary-side controller for synchro-
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^® compensa-
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.
, 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.
TYPICAL APPLICATIO
36V-72V to 3.3V/20A Isolated Forward Converter
V_IN+
1µF
100V
x3
V_IN–
Si7852DP
MURS120
T1
••
Si7852DP
Si7336ADP
30mΩ
1W
MURS120
2mΩ
2W
FQT7N10
100k
BAS21 ^0.22µF
L1: COILCRAFT SER2010-122
T1: PULSE PA0807
T2: PULSE PA0297
365k
1%
NDRV
UVLO
BOOST TG TS BG IS
FB/IN⁺
T2
••
1µF
2.2µF
25V
V_CC
SS/FLT
LTC3705
FS/IN^–
15k
1%
33nF
GND PGND VSLMT
162k
33nF
CMPSH1-4
Si7336ADP
×2
L1
1.2Ω 1.2µH
5k
FZT690B
10µF
7.5V
25V
2.2µF
V_OUT+
330µF
6.3V
×3
V_OUT–
I_S– ^FG
I_S+
PT⁺
SW SG
V_CC
LTC3726
PT^–
RUN/SS GND PGND SLP
FS/SYNC
FB/PHASE
ITH
MODE
680pF
20k
102k
1%
22.6k
1%
3726 TA01
3726fb
1