1 Features
1• Prebiased Start-up
• 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
• 1-MHz Capable Switching Frequency
• 1% Accurate Cycle-by-Cycle Overcurrent
Protection with Matched Duty Cycle Outputs
• Programmable Soft-Start and Hiccup Restart
Timer
• Thermally Enhanced 4-mm × 4-mm QFN-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 UCC28250 PWM controller is designed for high
power density applications that may have stringent
prebiased start-up requirements. The integrated
synchronous rectifier control outputs target highefficiency
and high-performance topologies such as
half-bridge, full-bridge, interleaved forward, and pushpull.
The UCC27200 half-bridge drivers and
UCC2732X MOSFET drivers used in conjunction with
the UCC28250 provide a complete power converter
solution.
Externally programmable soft-start, used in
conjunction with an internal prebiased start-up circuit,
allows the controller to gradually reach a steady-state
operating point under all output conditions. The
UCC28250 can be configured for primary or
secondary-side control and either voltage or current
mode control can be implemented.
The oscillator operates at frequencies up to 2 MHz,
and can be synchronized to an external clock. Input
voltage feedforward, cycle-by-cycle current limit, and
a programmable hiccup timer allow the system to
stay within a safe operation range. Input voltage,
output voltage and temperature protection can be
implemented. Dead time between primary-side switch
and secondary-side synchronous rectifiers can be
independently programmed.