This document introduces UCC28521/28 combination PFC/PWM controllers, which provide complete control functionality for any off-line power system requiring compliance with the IEC1000−3−2 harmonic reduction requirements. By combining the control and drive signals for the PFC and the PWM stages into a single device, significant performance and cost benefits are gained. Based on the UCC28511, the new devices employ an average current mode control architecture with input voltage feedforward. The major difference of the UCC28521/28 is that it uses trailing-edge PFC and trailing-edge PWM modulation, which provides higher switching speed.
The UCC28521 and UCC28528 are advanced PFC/PWM combination controllers that integrate power factor correction and PWM stages in a single device. They feature trailing‑edge modulation, built‑in sequencing, and high‑current gate drivers for both stages.
The document provides detailed electrical characteristics, pin functions, mechanical dimensions, and package options for the 20‑pin DW package, along with application notes for high‑efficiency server, desktop, and telecom AC‑DC converters.
| Supply voltage (VCC) | 12 V |
|---|---|
| Gate drive source current | 2 A |
| Gate drive sink current | 3 A |
| Operating temperature range | -40 °C to +105 °C |
| Maximum duty‑cycle | up to 100 % |
| Package type | 20‑pin DW (tape & reel available) |
The UCC28521 uses trailing‑edge/trailing‑edge (TEM/TEM) modulation for both the PFC and PWM stages.
The PWM turn‑on reference voltage is typically 6.30 V (typical 6.75 V, max 7.30 V).
The gate driver can source up to 2 A.
Both devices are offered in a 20‑pin DW (plastic small‑outline) package, available taped and reeled.