UCC2897 Current Mode Active Clamp PWM Controller | TI.com

This product continues to be in production to support existing customers.
Current Mode Active Clamp PWM Controller


Not Recommended for New Designs (NRND)

Replaced By UCC2897A – The device is an EXACT EQUIVALENT in functionality and parametrics to the compared device.

TI does not recommend using this part in a new design. This product continues to be in production to support existing customers.


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 DMAX 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.


  • Ideal for Active Clamp/Reset Forward, Flyback and Synchronous Rectifier Apps
  • Provides Complementary Auxiliary Driver with Programmable Deadtime (Turn-On Delay) between AUX and MAIN Switches
  • Peak Current-Mode Control with 0.5-V Cycle-by-Cycle Current Limiting
  • Hiccup Mode 0.75-V Current Limit
  • TrueDrive™ 2-A Sink, 2-A Source Outputs
  • 110-V Input Startup Device
  • Trimmed Internal Bandgap Reference for Accurate Line UV and Line OV Threshold
  • Programmable Slope Compensation
  • High-Performance 1.0-MHz Synchronizable Oscillator with Internal Timing Capacitor
  • Precise Programmable Maximum Duty Cycle
  • PB-Free Lead Finish Package
    • High-Efficiency DC/DC Power Supplies
    • Server Power, 48-V Telecom, Datacom, and 42-V Automotive Applications