UCC2891, UCC2892
UCC2893, UCC2894
SLUS542A − OCTOBER 2003 − REVISED JULY 2004
CURRENT MODE
ACTIVE CLAMP PWM CONTROLLER
FEATURES
D
Ideal for Active Clamp/Reset Forward,
D
D
D
D
D
D
D
D
D
Flyback Converters
Provides Complementary Auxiliary Driver
with Programmable Deadtime (Turn-On
Delay) between AUX and MAIN Switches
Peak Current-Mode Control with
Cycle-by-Cycle Current Limiting
110-V Input Startup Regulator on UCC2891/3
TrueDrivet 2-A Sink, 2-A Source Outputs
Accurate Line UV and Line OV Threshold
Programmable Slope Compensation
1.0-MHz Synchronizable Oscillator
Precise Programmable Maximum Duty Cycle
Programmable Soft Start
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.
APPLICATIONS
D
150-W to 700-W SMPS
D
High-Efficiency, Low EMI/RFI Off-Line or
D
D
DC/DC Converters
Server, 48-V Telecom, Datacom
High Power Adapter, LCD-TV and PDP-TV
BIAS
WINDING
16
15
14
13
Q2
5
6
7
8
SYNC
GND
CS
RSLOPE
AUX
PGND
SS/SD
FB
12
11
10
9
RF
CCLAMP
1
2
3
4
UCC2891
VIN
RDEL
RTON LINEUV
RTOFF
VREF
VDD
OUT
+VIN
LOAD
CBULK
Q1
SR
DRIVE
RCS
SECONDARY
SIDE E/A
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.
Copyright
2003, Texas Instruments Incorporated
www.ti.com
1
TI [ TEXAS INSTRUMENTS ]
