UCC2897A Datasheet, PDF (1/40 Pages) Texas Instruments – ADVANCED CURRENT-MODE ACTIVE CLAMP PWM CONTROLLER

UCC2897A
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SLUS829B − AUGUST 2008 − REVISED DECEMBER 2008
ADVANCED CURRENTĆMODE
ACTIVE CLAMP PWM CONTROLLER
FEATURES
D Low Output Jitter
D “Soft Stop” shut down of MAIN and AUX
D 110-V Input Startup Function
D Ideal for Active Clamp/Reset Forward,
Flyback and Synchronous Rectifier Uses
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 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
DESCRIPTION
The UCC2897A PWM controller simplifies
implementation of the various active clamp/reset
and synchronous rectifier switching power
topologies.
The UCC2897A 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,
VIN.
The UCC2897A adds a second level hiccup mode
current sense threshold, bi-directional
synchronization and input overvoltage protection
functionalities. The UCC2897A is offered in 20-pin
TSSOP (PW) and 20-pin QFN (RGP) package.
TYPICAL APPLICATION DIAGRAM
RDEL
3
RON
4
ROFF
5
6
CVREF ₇
8
CF
9
RSLOPE
10
UCC2897A
RDEL
VIN 1
LINEOV 19
RON
LINEUV 18
ROFF
VDD 17
VREF
PVDD 16
SYNC
GND
OUT 15
CS
AUX 14
RSLOPE PGND 13
BIAS
WINDING
+VIN
CBIAS
ROUT
Q1
CAUX
DAUX _Q2
CSS
12 SS/SD
FB 11
Q4
D3
LO
D4 _CO
Q3
SR
D1
DRIVE
LOAD
SECONDARY
SIDE E/A
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
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  2008, Texas Instruments Incorporated
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