February 2013

DocID018573 Rev 2

1/32

UM1063

User manual

EVALPM8803-FLY: IEEE802.3at compliant demonstration kit with

synchronous flyback converter

By Antonio Rotta

Introduction

The PM8803 is a highly integrated device embedding an IEEE802.3at-2009 compliant

powered device (PD) interface together with a PWM controller and support for auxiliary

sources.

Figure 1 is an image of the EVALPM8803-FLY PoE+ demonstration board. The

same PCB can be populated with different components to support various configurations

and topologies (synchronous flyback with or without active clamp, flyback with diode

rectification).

This document focuses on a reference design for PoE+ based on flyback topology with

synchronous rectification, with the PM8803 as the main controller.

The schematics and board layout of the PoE+ converter are given in

Section 2 and 3 while

the related bill of material is detailed in

Section 5. In Section 7 efficiency measurements

together with main waveforms of the PoE interface and flyback converter are shown.

Figure 1. EVALPM8803-FLY demonstration kit

www.st.com