aerobotics

5V/20A, Active Clamp Forward Converter, Power over Ethernet (PoE) - IEEE 802.3bt Compliant Reference Design

STEVAL-POE003V1

Overview

This reference design represents a PoE Class 8 converter designed for high efficiency conversion over a wide load range. It is based on the PM8805 PoE-PD interface compliant with the IEEE802.3bt standard, and a DC-DC forward active clamp converter driven by the PM8804 PWM controller.

The PM8805 system on package device embeds two active bridges and an IEEE802.3bt compliant Powered Device (PD) interface. It can be used in all medium-to-high power 2P and 4P high efficiency PoE and PoE+ applications such as point of sales and retail logistics devices.
The PM8804 PWM controller represents an integrated solution for a smart and efficient 48 V converter, including a programmable oscillator for the switching frequency, adjustable slope compensation, dual complementary low-side drivers with programmable dead time, programmable soft start, soft turn off and a programmable current sense blanking time.

Main features

Features of PM8805 PoE-PD interface
- System in package integrating a double active bridge, hot-swap MOSFET and PoE-PD interface
- PoE-PD single-signature interface compliant with IEEE 802.3bt
- Detection and support of high power 4-pair applications
- 100 V N-Ch MOSFETs with 0.2 Ω total path resistance for each active bridge
- Identifies which kind of PSE (standard or legacy) it is connected to and provides successful IEEE802.3.af/at/bt classification indication through a combination of the T0, T1 and T2 signals (open drain)
- VFQFPN43 8x8 mm with 6 exposed pads
Features of PM8804 PWM controller
- PWM peak current mode controller
- Input operating voltage up to 75 V
- Internal high voltage start up regulator with 20 mA capability
- Programmable fixed frequency up to 1 MHz
- Soft start up with settable time
- Soft turn off (optionally disabled)
- Dual 1Apk, low side complementary gate drivers
- GATE2 optionally turned off for reduced consumption
- 80% maximum duty cycle with internal slope compensation
- VFQFPN 3.0x3.0x1.0 16L 0.5 mm pitch
WEEE compliant
RoHS compliant

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:2025-06-20 12:46:58

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