STMicroelectronics’ PM8805 is a system-in-package which provides a smart power supply to Power-over-Ethernet (PoE) Powered Devices (PDs) consuming up to 99.9W.
The PM8805 consists of two active bridges and their drivers, a charge pump to drive the high-side MOSFETs, a hot-swap MOSFET, and an IEEE 802.3bt/at/af standard-compliant Ethernet interface. The device performs physical layer classification to correctly identify the type of Power-Sourcing Equipment (PSE) to which it is connected.
The MOSFET in each active bridge is a 100V N-channel device which features 0.2Ω total path resistance. The hot-swap MOSFET is a 100V high-side N-channel device with 0.1Ω resistance.
The PM8805 works with power either from the Ethernet cable or from an external power source such as a wall adapter. It is ideal as the interface section of PoE switch-mode power supplies which are required to meet very high efficiency targets.
It provides a PGD signal which can be used to enable a PWM controller, a DC-DC converter or an LED driver.
Free Development Boards
The STEVAL-POE002V1 reference design is a two-stage converter for a powered device. It can provide up to 40W at 5V DC/8A from an appropriate four-pair PSE or an external auxiliary supply.
The STEVAL-POE005V1 reference design is a 12V DC/8A converter with a PoE-PD interface and a DC-DC active clamp forward converter.
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