LTC3765_15 Datasheet, PDF (1/24 Pages) Linear Technology – Active Clamp Forward Controller and Gate Driver

FEATURES
n _{Supports Self-Starting Secondary-Side Control}
n _{Direct Flux Limit™ Guarantees No Saturation}
n _{Active Clamp Drive with Delay Adjustment}
n _{On-Chip Bridge Rectifier Eliminates Need for}
Separate Gate Drive Bias Supply
n _{Wide Input Supply Range: 8V and Up (Limited Only}
by External Components)
n _{Linear Regulator Controller for Fast Start-Up}
n _{High Speed Gate Drivers}
n _{Precision UVLO with Adjustable Hysteresis}
n _{Overcurrent Protection}
n _{Overtemperature Protection}
n _{Adjustable Start-Up Frequency and Soft-Start}
n _{Tiny 16-Lead MSOP Package}
APPLICATIONS
n _{Isolated Battery Chargers}
n _{Isolated 48V Telecommunication Systems}
n _{Servers and Embedded Computing}
n _{Automotive and Heavy Equipment}
LTC3765
Active Clamp Forward
Controller and Gate Driver
DESCRIPTION
The LTC^®3765 is a start-up controller and gate driver for
use in a self-starting secondary-side control forward con-
verter. When combined with the LTC3766 secondary-side
synchronous forward controller, a complete isolated power
supply is created using a minimum of discrete parts. A
proprietary scheme is used to multiplex gate drive signals
and bias power across the isolation barrier through a
small pulse transformer. The LTC3765 contains an on-
chip bridge rectifier that extracts gate drive bias power
from this pulse transformer, eliminating the need for a
separate bias supply. A precision undervoltage lockout
circuit and linear regulator controller ensure a quick and
well-controlled start-up.
The LTC3765 includes an active clamp output for driving an
external PMOS, as well as an adjustable delay to optimize
efficiency. The active clamp architecture reduces voltage
stress on the main power switch, and provides the highest
possible efficiency. Overcurrent protection and the Direct
Flux Limit guarantee no transformer saturation without
compromising transient response.
L, LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo are registered trademarks
and Direct Flux Limit is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents, including 7200014 and
6144194. Other patents pending.
TYPICAL APPLICATION
36V-72V to 5V/15A Active Clamp Isolated Forward Converter
V_IN+
36V TO 72V
T1
6:2
••
L1
1.4µH
2.2µF
100V
×3
FDMS86201
33nF
200V
100nF
200V
BSC0901NS
SiR414DP
L1: PULSE PA1393.152
T1: PULSE PA0810
T2: PULSE PA0297
V_IN–
365k
1/8W
4.7µF
15k
15mΩ _168Ω
0.5W
3mΩ
2W
100k
Si3440DV
Si3437DV 2.2nF
(SOT-23) 250VAC ^{100Ω 100Ω}
1Ω
1nF
NDRV PG I_S+ I_S– AG I_SMAG
RUN
IN⁺
V_CC
LTC3765
IN^–
SSFLT
R_CORE
FS/UV
DELAY SGND PGND
33nF 10.5k
14k
0.1µF _T2 1.0µF
2:1
••
18.2k
FG SW SG RUN V_IN NDRV V_CC FS/SYNC V_S+ V_S–
I_S–
I_S+
FB
PT⁺
LTC3766
ITH
PT^–
SS
GND PGND I_PK
SGD FGD MODE
33nF
26.1k 15k 22k
47pF
4.42k
604Ω
470pF
17.8k
For more information www.linear.com/LTC3765
V_OUT+
5V
15A
220µF
6.3V
×2
V_OUT–
3765 TA01
3765fb
1