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STMicroelectronics PM8805 | Demoboard STEVAL-POE006V1

3.3V/20A, active clamp forward converter, Power Over Ethernet (PoE) IEEE 802.3bt compliant reference design

Overview

TopologyOther Topology
Input voltage3.3 V
IC revisionRev 3

Description

The PM8805 is a system-in-package for smart power supply of Power over Ethernet (PoE) Powered Devices (PD) and it is applicable for power level up to 99.9 W.It embeds: two active bridges and their driving circuitry, a charge pump to drive the high-side MOSFETs, the hot swap MOSFET and the interface compliant with IEEE 802.3bt.The device performs the physical layer classification, providing the indication of successful PSE type identification. A 4-pair PSE is identified and the information is available by a dedicated matrix of Tx signals.The device works with power either from the Ethernet cable or from an external power source such as a wall adapter, with possible prevalence of the auxiliary source with respect to the PoE.The PM8805 is suitable to build the interface section of PoE switch mode power supplies targeting the highest conversion efficiency. It provides a PGD signal that can be used to enable a PWM controller, a DC-DC converter or an LED driver.

Features

  • 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) it is connected to and provides successful IEEE 802.3af/at/bt classification indication as a combination of the T0, T1 and T2 signals (open drain)
  • Smart operation mode selection through the STBY, FAUX and RAUX control signals
  • QFN 56 8x8mm package with 43 pins and 6 exposed pads
  • 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 startup with settable time
  • Soft turn off (optionally disabled)
  • Dual 1 APK, low side complementary gate drivers
  • GATE2 can be turned off for reduced consumption
  • 80% maximum duty cycle with internal slope compensation
  • QFN 16 3x3mm package with exposed pad

Typical applications

  • PoE lighting systems
  • High power wireless data systems / Security cameras / Access points / Public information displays
  • various applications including wireless access points, supplied with a PoE-PD interface and a DC-DC active clamp forward converter

Products

Order Code Data­sheet Downloads Product seriesRDC
(mΩ)
IR
(A)
ISAT
(A)
fres
(MHz)
TypeWinding StyleNumber of windingsL1
(µH)
Zmax
(Ω)
IR 1
(mA)
RDC1 max.
(Ω)
VR
(V)
Data rateNumber of PortsPoEHPLEOperating TemperatureVT
(V (AC))
MountL
(µH)
LSmin.
(nH)
Samples
74439346056
STE ALT EAG CAD LTS PSP SPE IGS CADWE-XHMI SMT Power Inductor 15 6.9 13.6 22 1 -40 up to +125 °C SMT 5.6
744272471
STE ALT EAG CAD LTS PSP IGS CAD SPAWE-SL5 SMT Common Mode Line Filter 1.6 sectional 2 470 1750 1600 0.065 80 1000 SMT 470 3000
7490220123
STE ALT EAG CAD LTS PSP CAD IGS SPAWE-LAN LAN Transformer 4PPoE (to 1400 mA) 200 1000 Base-T 1 4PPoE (up to 1500 mA) No -40 up to +105 °C 1500 SMT 200
Order Code Data­sheet
74439346056
744272471
7490220123
Samples
Order Code Data­sheet Downloads Product seriesRDC
(mΩ)
IR
(A)
ISAT
(A)
fres
(MHz)
TypeWinding StyleNumber of windingsL1
(µH)
Zmax
(Ω)
IR 1
(mA)
RDC1 max.
(Ω)
VR
(V)
Data rateNumber of PortsPoEHPLEOperating TemperatureVT
(V (AC))
MountL
(µH)
LSmin.
(nH)
Samples