STMicro’s Advanced Chipset Brings 100W PoE Standard to Connectivity and Smart-Building Apps

April 8, 2019 Alix Paultre

A chipset from STMicroelectronics lets users build Powered Devices (PDs) compliant with the IEEE 802.3bt Power-over-Ethernet (PoE) specification. The PM8804 and PM8805 provide the PoE-converter circuitry for PDs up to class-8, which defines a usable power budget of 71 Watts. 

The PM8804 implements a complete PWM controller for a 48V isolated flyback or forward converter, including dual low-side gate drivers for high-efficiency forward active-clamp topologies. The operating frequency is selectable up to 1MHz, and the device features a high-voltage startup regulator with 20mA output capability.

The PM8805 companion chip contains two active bridges, a charge pump for driving high-side MOSFETs, a hot-swap FET, and the IEEE 802.3bt compliant interface. The PM8805 generates a Power-good signal for enabling the PM8804 and other circuitry such as an LED driver, and supports Maintain Power Signature (MPS) current control that allows the PD to enter power-saving standby without being disconnected.

The PM8804 is packaged as a 3mm x 3mm, 0.5mm-pitch VFQFPN-16, and priced at $0.60 for orders of 1,000 pieces. The PM8805 in 8mm x 8mm thermally enhanced VFQFPN-43 featuring exposed pads is $4.50.

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