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5V/8A synchronous flyback converter, IEEE 802.3bt compliant Power over Ethernet (PoE) reference design

STEVAL-POE002V1

Overview

The STEVAL-POE002V1 reference design is a two-stage converter for a powered device (PD), and is able to deliver up to 40 W (5 V/8 A) DC from appropriate 4-pair PoE power sourcing equipment (PSE), or an external auxiliary supply.

The first stage is the Ethernet interface is based on the PM8805 controller with integrated full active bridge rectification. The PoE controller is compliant with the third generation IEEE 802.3bt specification (as well as the preceding 802.3af/at standards), with improved features and increased power capacity that allow new application possibilities for PoE networks, including point of sales and retail logistics devices.
The second stage is the DC-DC converter designed around a fixed frequency flyback topology managed by the configurable PM8804 PWM controller, with secondary synchronous rectification via a gate driver transformer.

Main features

PM8805 4-pair IEEE 802.3bt compliant PD interface
Works with power supplied from Ethernet LAN cables or local auxiliary sources
Line input voltage range: 40 to 60 V_DC
Output stage managed by configurable PM8804 controller
Output voltage: 5 V_DC ±2.5%
Output current: 8 A

Peak-to-peak output ripple:
DC-DC full load efficiency: >91%
Overall full load efficiency: >90%
Transient response ΔV pk-pk 100% to 50% load step ≈ 700 mV
Switching frequency ≈ 280 KHz

Design Files

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It is your responsibility to test the circuit yourself and determine its suitability for you. EEWorld will not be liable for direct, indirect, special, incidental, consequential or punitive damages arising from any cause or anything connected to any reference design used.

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Update:2025-05-08 17:52:59

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