12V/8A, active clamp forward converter, Power Over Ethernet (PoE) IEEE 802.3bt compliant reference design

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Parameter NameParameter Value
Target ApplicationLED Lighting
Core ProductPM8804, PM8805
Packing TypeNot Applicable
RoHs compliantEcopack2
Package NameCARD

This reference design represents a 12 V, 8 A converter solution ideal for various applications including building safety and security or surveillance, with a PoE-PD interface and a DC-DC active clamp forward converter.

The PoE-PD interface is based on the PM8805 system in package device with two active bridges and an IEEE 802.3bt compliant Powered Device (PD) interface. It can be used in all medium-to-high power 2P and 4P high efficiency PoE and PoE+ applications.

The DC-DC active clamp forward converter is designed around the PM8804 PWM controller, which is an integrated solution for smart and efficient 48 V converters, featuring 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.

Key features
  • Features of the PM8805 PoE-PD interface:
    • System in package integrating a double active bridge, a hot-swap MOSFET and a PoE-PD
    • Supports legacy 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) is connected to, and provides successful IEEE802.3 af /at /bt classification indication as combination of the T0, T1 and T2 signals (open drain)
    • Smart operational mode selection through the STBY, FAUX and RAUX control signals
    • QFN 56 8x8mm package with 43 pins and 6 exposed pads
  • Features of the 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 adjustable time
    • Soft turn off (optionally disabled)
    • Dual 1 APK, low side complementary gate drivers
    • GATE2 optionally turned off for reduced consumption
    • 80% maximum duty cycle with internal slope compensation
    • QFN 16 3x3mm package with exposed pad