The UCC28251 PWM controller is designed for high power density applications that may have
stringent prebiased startup requirements. The UCC28251s 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
Externally programmable soft-start, used in conjunction with an internal pre-biased
startup circuit, allows the controller to gradually reach a steady-state operating point under all
output conditions. The UCC28251 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 1.8 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.