UCC2891 Datasheet, PDF (1/34 Pages) Texas Instruments – CURRENT MODE ACTIVE CLAMP PWM CONTROLLER

UCC2891, UCC2892
UCC2893, UCC2894
ą
SLUS542A − OCTOBER 2003 − REVISED JULY 2004
CURRENTĆMODE
ACTIVE CLAMP PWM CONTROLLER
FEATURES
D Ideal for Active Clamp/Reset Forward,
Flyback Converters
D Provides Complementary Auxiliary Driver
with Programmable Deadtime (Turn-On
Delay) between AUX and MAIN Switches
D Peak Current-Mode Control with
Cycle-by-Cycle Current Limiting
D 110-V Input Startup Regulator on UCC2891/3
D TrueDrivet 2-A Sink, 2-A Source Outputs
D Accurate Line UV and Line OV Threshold
D Programmable Slope Compensation
D 1.0-MHz Synchronizable Oscillator
D Precise Programmable Maximum Duty Cycle
D Programmable Soft Start
APPLICATIONS
D 150-W to 700-W SMPS
D High-Efficiency, Low EMI/RFI Off-Line or
DC/DC Converters
D Server, 48-V Telecom, Datacom
D High Power Adapter, LCD-TV and PDP-TV
DESCRIPTION
The UCC2891/2/3/4 family of PWM controllers is
designed to simplify implementation of the various
active clamp/reset switching power topologies.
The UCC289x is a peak current-mode, fixed-
frequency, high-performance pulse width modulator.
It includes the logic and the drive capability for the
auxiliary switch with a simple method of
programming the critical delays for proper active
clamp operation.
The UCC2891/3 includes a 110-V start-up
regulator for initial start-up and to provide
keep-alive power during stand-by.
Additional features include an internal
programmable slope compensation circuit,
precise D_MAX limit, and a single resistor
programmable synchronizable oscillator. An
accurate line monitoring function also programs
the converter’s ON and OFF transitions with
regard to the bulk input voltage. Along with the
UCC2897, this UCC289x family allows the power
supply designer to eliminate many of the external
components, reducing the size and complexity of
the design.
UCC2891
1 RDEL
VIN 16
2 RTON LINEUV 15
3 RTOFF VDD 14
4 VREF OUT 13
5 SYNC
AUX 12
6 GND PGND 11
7 CS
SS/SD 10
8 RSLOPE FB 9
BIAS
WINDING
+VIN
CBULK
CCLAMP
Q1
Q2
RCS
RF
SR
DRIVE
SECONDARY
SIDE E/A
LOAD
UDG−02162
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
www.ti.com
Copyright  2003, Texas Instruments Incorporated
1