UCC2897_15 Datasheet, PDF (1/40 Pages) Texas Instruments – ADVANCED CURRENT-MODE ACTIVE CLAMP PWM CONTROLLER

UCC2897
ą
SLUS591G − NOVEMBER 2003 − REVISED DECEMBER 2008
ADVANCED CURRENTĆMODE
ACTIVE CLAMP PWM CONTROLLER
FEATURES
D Ideal for Active Clamp/Reset Forward,
Flyback and Synchronous Rectifier Apps
D Provides Complementary Auxiliary Driver
with Programmable Deadtime (Turn-On
Delay) between AUX and MAIN Switches
D Peak Current-Mode Control with 0.5-V
Cycle-by-Cycle Current Limiting
D Hiccup Mode 0.75-V Current Limit
D TrueDrivet 2-A Sink, 2-A Source Outputs
D 110-V Input Startup Device
D Trimmed Internal Bandgap Reference for
Accurate Line UV and Line OV Threshold
D Programmable Slope Compensation
D High-Performance 1.0-MHz Synchronizable
Oscillator with Internal Timing Capacitor
D Precise Programmable Maximum Duty Cycle
D PB-Free Lead Finish Package
APPLICATIONS
D High-Efficiency DC/DC Power Supplies
D Server Power, 48-V Telecom, Datacom, and
42-V Automotive Applications
TYPICAL APPLICATION DIAGRAM
DESCRIPTION
The UCC2897 PWM controller simplifies
implementation of the various active clamp/reset
and synchronous rectifier switching power
topologies.
Based on the UCC2891 active-clamp controller
the UCC2897 is a peak current-mode, fixed-
frequency, high-performance pulse width modulator.
It includes the logic and the drive capability for the
P-channel auxiliary switch along with a simple
method of programming the critical delays for
proper active clamp operation.
Features include an internal programmable slope
compensation circuit, precise D_MAX limit, and a
synchronizable oscillator with an internal timing
capacitor. An accurate line monitoring function
also programs the converter’s ON and OFF
transitions with regard to the bulk input voltage.
The UCC2897 adds a second level hiccup mode
current sense threshold, bi-directional
synchronization and the input overvoltage
protection functionalities that are not available on
the 16-pin UCC2891. The UCC2897 is offered in
20-pin TSSOP (PW) and 20-pin QFN (RTJ)
package.
UCC2897
3 RDEL
VIN 1
LINEOV 19
4 RTON
LINEUV 18
5 RTOFF
VDD 17
6 VREF
PVDD 16
7 SYNC
8 GND
15
OUT
BIAS
WINDING
CBULK
+VIN
CCLAMP
Q1
Q2
SR
DRIVE
LOAD
9 CS
AUX 14
10 RSLOPE PGND 13
12 SS/SD
FB 11
RCS
RF
SECONDARY
SIDE E/A
UDG−03186
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.
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Copyright  2006 − 2008, Texas Instruments Incorporated
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