UCC2897A Advanced Current-Mode Active-Clamp PWM Controller

1 Features

• Low-output jitter
• Soft-stop shutdown of MAIN and AUX
• 110-V input startup function
• Ideal for active-clamp, reset-forward, flyback and synchronous rectifier uses
• Provides complementary auxiliary driver with programmable dead time (Turn-On Delay) between AUX and MAIN switches
• Peak current-mode control with 0.5-V cycle-by-cycle current limiting
• TrueDrive™ 2-A Sink, 2-A source outputs
• Trimmed internal-bandgap reference for accurate line UV and line OV threshold
• Programmable slope compensation
• High-performance 1-MHz synchronizable oscillator with internal timing capacitor
• Precise programmable maximum duty cycle
• PB-free lead finish package

2 Applications

• High-efficiency DC-to-DC power supplies
• Server power, 48-V telecom, datacom, and 42-V automotive applications

3 Description

The UCC2897A PWM controller simplifies implementation of the various active clamp or reset and synchronous rectifier switching power topologies.

The UCC2897A is a peak current-mode fixed-frequency high-performance pulse-width modulator. The controller 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 ON and OFF transitions of the converter 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) packages.

1. For all available packages, see the orderable addendum at the end of the datasheet.

Device Images

Typical Application Diagram