AN2783 Datasheet, PDF (1/47 Pages) STMicroelectronics – PM8800 demonstration kit for standard and high power PoE

AN2783
Application note
PM8800 demonstration kit for standard and high power PoE
PD interface and power supply, with auxiliary sources
Introduction
This document details the characteristics and performances of the PM8800 demonstration
kit which has been designed to cover a broad range of power over Ethernet (PoE)
applications. PM8800 is a highly integrated device embedding an IEEE802.3af compliant
powered device (PD) interface together with a PWM controller and support for auxiliary
sources.
Even though PM8800 can be configured to work in both isolated and non-isolated
topologies, this application note focuses on an isolated topology only, in two different output
power configurations (10 W and 20 W) and 2 different output voltages (5 V and 3.3 V).
The PM8800 demonstration kit supports diode as well as synchronous rectification.
Auxiliary sources can be connected to the board on 2 input points. One input allows
prevalence of the auxiliary sources with respect to the PoE, while the other input allows the
usage of a wall adaptor with voltage lower than the internal PoE UVLO threshold and still
benefits from the inherent inrush and DC current limit.
The above mentioned configurations are all supported by the PM8800 demonstration kit as
options on the same PCB. The bill of material (BOM) (see Section 5 on page 12) provides
the list of components to be mounted for each of the targeted configurations.
Figure 1. PM8800 demonstration kit
The high-power board appears on the left of the photo and standard board is on the right.
September 2008
Rev 2
1/47
www.st.com