Increases power budget according to IEEE802.3bt standard and maintains backward compatibility with existing equipment

Analog Devices announced the development of the LT4294 IEEE 802.3bt PD (Powered Device) interface controller for applications requiring up to 71W of supply power.

The new PoE (Power over Ethernet) standard IEEE 802.3bt not only must increase the power budget to implement new applications and features, but must simultaneously support 10 gigabit Ethernet (10GBASE-T) and maintain backward compatibility with existing IEEE 802.3af and 802.3at PoE equipment.

The LT4294 PD controller, which complies with IEEE 802.3bt Draft 2.3 and is combined with the LT4321 PoE ideal diode bridge controller, delivers up to 99% of power from the RJ-45 connector to hot-swap outputs, and supports newly added features including different PD classes (5, 6, 7, 8), PD types (Type 3 and Type 4), and 5-event classification.

The LT4294 is a single-signature 802.3bt PD controller that can be connected to any high-efficiency switching regulator. Single-signature PD eliminates the need for secondary PD controllers, reducing system cost and complexity. Additionally, it offers excellent switcher flexibility regardless of whether isolated or non-isolated switches are used, enabling immediate deployment and allowing the use of proprietary power solutions.

Unlike conventional PD controllers that integrate power MOSFETs, the LT4294 applies external MOSFETs to reduce overall PD heat dissipation and maximizes power efficiency, which is particularly important at power levels of 802.3bt and above. The external MOSFET architecture allows users to size MOSFETs according to their application requirements. Standard LT4294-based implementations typically require MOSFETs with low RDS(ON) values around 30mΩ.