STMicroelectronics Announces Power-over-Ethernet Chipset for 5G and Smart-Building Applications

April 05, 2019 by Gary Elinoff

The chipset utilizes the latest IEEE 802.3bt Power-over-Ethernet (PoE) specification for powered devices.

The PM8804 and PM8805 from STMicroelectronics use the latest IEEE 802.3bt Power-over-Ethernet (PoE) specification, creating a reliable and space-efficient solution for Powered Devices (PDs).

The new Power over Ethernet (PoE) chipset will provide the PoE-converter circuitry for PDs up to class-8, which defines a usable power budget of 71 Watts. The devices obviate the need for engineers to “reinvent the wheel” every time a remote device needs to be designed to be powered via its Ethernet cable, and with the advent of 5G, the need will be huge and ubiquitous.

5G Small Cells

The growth of 5G will make PoE chips especially useful, due to the nature of 5G. The millimeter wave signals that 5G employs don’t penetrate objects as readily as the much longer wavelength used by 4G. The solution is large numbers of strategically deployed 5G “small cell” towers to supplement large, traditional cell towers. 


The PM8804 and PM8805 PoE chipset. Image courtesy STMicroelectronics.


The PM8804 and PM8805 will also find use in other remote equipment that will also need to be cheaply and efficiently powered over Ethernet cables. These include smart-building applications such as IP cameras, access control systems, display panels, lighting, curtain or shutter controllers, video-call systems, IP phones, and tabletop consoles.

The PM8804

The PM8804 is a PWM controller with an embedded dual active bridge that integrates the circuitry required to design smart and efficient 48 Volt flyback converters.


Block Diagram for the STM8804. Image courtesy STMicroelectronics datasheet. 


The STM8804 is a pulse-width modulated peak current controller with a programmable fixed frequency of up to 1 MHZ. It can accommodate input operating voltages of up to 75 volts.

Embedded protections include:

  • Severe overcurrent protection with latch after 4 events
  • Delayed overload protection with automatic restart
  • Feedback disconnection (OV) protection on VC
  • Thermal shutdown

The PM8804 is packaged as a 3mm x 3mm, 0.5mm-pitch VFQFPN-16.

The PM8805

The PM8805 is the companion chip to the PM8804 and is applicable for power levels up to 99.9 watts. The device performs the physical layer classification, and identifies successful PSE (power sourcing equipment) identification for both standard and legacy types.

The unit features:

  • Dual active bridge, hot swap MOSFET and PoE-PD interface in a system-in-package (SiP)
  • 100 V N-ch MOSFETs with 0.2 Ω total path resistance for each active bridge.
  • 100 V, 0.1 Ω high-side N-channel hot swap MOSFET
  • Two-step hot swap current protection: DC with 1 ms delay and short-circuit with 10 us delay.
  • Thermal protection shut-down


Block Diagram for the STM8804. Image courtesy STMicroelectronics datasheet. 


The PM8805 is packaged as an 8mm x 8mm thermally enhanced VFQFPN-43 with exposed pads.

What the Competition has to Offer

Given the wide range of applications for PoE devices, it isn’t surprising that STM’s offerings do not stand alone.

Microsemi’s Line of PoE and PD devices include units with and without PWM controllers. And Analog Devices' PSE controllers have the ability to detect and classify PDs. They have built-in capabilities to source the correct amount of power to the PD over Ethernet cables, and they support multiple power levels over Ethernet including:

  • IEEE PoE (13W, 802.3af)
  • IEEE PoE+ (25.5W, 802.3at)
  • IEEE PoE++ (71.3W, 802.3bt
  • ADI LTPoE++ (90W) standard

Have you used PoE in any designs or applications? What other ways do you think 5g will change the way power is delivered? Share your thoughts in the comments.