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.