PD controller offers 99% efficiency reducing system cost and complexity

Linear Technology has announced the LT4294 IEEE 802.3bt Powered Device (PD) interface controller for applications requiring up to 71W of delivered power. This new PoE standard – IEEE 802.3bt – increases the power budget to enable new applications and features, while supporting 10 Gigabit Ethernet (10GBASE-T) and maintaining backward compatibility with older IEEE 802.3af and 802.3at PoE equipment. When combined with the PoE ideal diode bridge controller, the IEEE 802.3bt Draft 2.3 compliant PD controller provides up to 99% of power available from the RJ45 connector to the hot swap output while supporting newly introduced features, including additional PD classes (5, 6, 7 and 8), PD types (Type 3 and Type 4) and five-event classification. The device is a single-signature 802.3bt PD controller that can be married to any high efficiency switching regulator. A single-signature PD eliminates the need for a second PD controller, reducing system cost and complexity. Whether an isolated or non-isolated switcher is used, switcher flexibility supports the use of off-the-shelf and proprietary power solutions. Unlike traditional PD controllers that integrate the power MOSFET, the device controls an external MOSFET to drastically reduce overall PD heat dissipation and maximize power efficiency, especially important at 802.3bt’s higher power levels. An external MOSFET architecture allows users to size the MOSFET to their application’s requirements; standard LT4294-based implementations routinely select low RDS(ON) 30mohm MOSFETs. The device is offered in industrial and automotive grades, supporting operating temperature ranges from –40C to 85C and –40C to 125C, respectively.