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AN4319

Main characteristics and circuit description

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Main characteristics and circuit description

The main characteristics (reference and electrical specifications) of the converter are listed

in Table 2.

This document details the characteristics and performances of the PM8800A demonstration

kit STEVAL-TSP003V2 which has been designed to cover a broad range of power over

Ethernet (PoE) applications.

The PM8800A is a highly integrated device embedding an IEEE 802.3af compliant powered

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

Even though the PM8800A can be configured to work in both isolated and non-isolated

topologies, single or double output; this application note focuses on a low cost isolated

flyback converter topology with diode rectification, 12 V output voltage with up to 1 A output

current capability.

Auxiliary sources can be connected to the board on 2 input connectors. One input (AUX II)

allows prevalence of the auxiliary sources with respect to the PoE, while the other input

(AUX I) 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) in Table 3 provides the list of

components to be mounted to obtain a 12 V at 1 A demonstration board.

Table 1. Reference

Reference code

Device

PM8800A

Demonstration board

STEVAL-TSP003V2

Table 2. Electrical specification

Parameter

Specifications

Input voltage supplies VIN [VDC]

From 40 to 60 V at 13 W

Output voltage Vout [VDC]

12 VDC ± 5% at 1 A

Peak-to-peak output ripple

100 mV

Efficiency DC-DC full-load

> 88%

Efficiency overall peak

> 85%

Transient response

Voutpk-pk to 50% load step

< 200 mVpp

V in load line case

< 0.5%

GLOOP bandwidth

3.5 kHz

GLOOP phase margin at 0 dB

105 deg.

GLOOP dB margin at 0 deg.

-10 dB