Ratification of IEEE802.3bt powers new PSE/PD PoE opportunities

New IEEE802.3bt PoE standard opens the way for a whole suite of smart building and Internet of Things (IoT) devices connected and powered via RJ45 sockets.

It has been debated and mulled over for some time, but the IEEE802.3bt-2018 - IEEE Approved Draft Standard for Ethernet - Amendment 2: Power over Ethernet over 4 Pairs was finally ratified at the end of September. Significantly increasing the power sourcing equipment (PSE) minimum input power from 30 W, it can now deliver up to 60 W (Type 3) or 100 W (Type 4) by utilizing all four structured wiring pairs. This solves the challenge of higher power and more efficient PoE delivery systems while remaining fully backward compatible and offering data rates of up to 10GBASE-T.

So as well as enabling a whole suite of smart building and Internet of Things (IoT) applications, next-generation PSE/PD PoE systems will reduce infrastructure complexity and costs. Large LCD screens, LED lighting fixtures, wireless hot-spots and pan-tilt-zoom CCTV cameras, all connected and powered via RJ45 sockets. The new standard also extends the power classification information exchanged during the initial negotiation. Providing meaningful power management capabilities and supporting multiple and future PoE classes.

Of course, with the higher power levels of IEEE802.3bt comes the need to maximize power efficiency and significantly reduce overall power device heat dissipation. One way to achieve this is by employing a system architecture that uses external MOSFETs rather than having the MOSFET integrated into the control IC. This approach also allows the specification of the MOSFETs to be efficiently tuned to the needs of the specific application. Soft-start and ‘hot-swappable’ procedures also need to be considered along with resilience to short-circuits.

Nexperia’s dedicated Application Specific MOSFETs for Power over Ethernet (PoE) are specifically designed for high power PSE/PD PoE applications and they are housed in the compact (3 mm2) LFPAK33 industry leading package. These MOSFETs have the power capability to support the new IEEE802.3bt standard – with the PSMN075-100MSE recommended for PoE PSE/PD systems up to 60 W, and for up to 100 W the PSMN040-100MSE. Delivering best-in-class linear mode performance and power capability, they are the ideal choice when it comes to designing a high power PSE/PD solution.