1 Features

1• Prebiased Startup

• Synchronous Rectifier Control Outputs with

Programmable Delays (Including Zero Delay

Support)

• Voltage Mode Control with Input Voltage Feed-

Forward or Current Mode Control

• Primary or Secondary-Side Control

• 3.3-V, 1.5% Accurate Reference Output

• Lower Minimum Operating Frequency

• 1% Accurate Cycle-by-Cycle Over Current

Protection with Matched Duty Cycle Outputs

• Programmable Soft-Start and Hiccup Restart

Timer

• Thermally Enhanced 4-mm x 4-mm VQFN-20

Package and 20-pin TSSOP Package

2 Applications

• Half-Bridge, Full-Bridge, Interleaved Forward, and

Push-Pull Isolated Converters

• Telecom and Data-com Power

• Wireless Base Station Power

• Server Power

• Industrial Power Systems

3 Description

The UCC28251 PWM controller is designed for high

power density applications that may have stringent

prebiased startup requirements. The UCC28251’s

integrated synchronous rectifier control outputs target

high efficiency and high performance topologies such

as half-bridge, full-bridge, interleaved forward, and

push-pull. The UCC27210 half bridge drivers and

UCC2752x MOSFET drivers used in conjunction with

the UCC28251 provide a complete power converter

solution.

The UCC28251 is a functional variant of the

UCC28250 PWM Controller. While the same basic

functionality of the UCC28250 is largely maintained,

the UCC28251 is designed to enhance performance

in both offline, 400-V input DC-to-DC applications and

48-V input full-bridge or half-bridge applications.