LT4295 IEEE 802.3bt-powered device interface controller. Source: Linear Technology
The standard, also known as PoE++ or 4PPoE, increases the power budget to enable new applications and features, while supporting 10 Gigabit Ethernet (10GBASE-T) and maintaining backward compatibility with older IEEE equipment. The LT4295 is IEEE 802.3bt (Draft 2.0) compliant and supports newly introduced features, including all additional PD classes (5, 6, 7 and 8), additional PD types (Type 3 and Type 4) and five-event classification.
The LT4295 is a single-signature 802.3bt PD controller that integrates an isolated switching regulator controller, capable of synchronous operation in both high-efficiency forward and no-opto flyback topologies with auxiliary power support. This high level of integration simplifies front-end PD designs by reducing component count and board space, allowing the LT4295 to efficiently deliver power to PD loads using just one IC.
Unlike traditional PD controllers that integrate the power MOSFET, the LT4295 controls an external MOSFET to significantly reduce overall PD heat dissipation and maximize power efficiency, particularly important at the higher power levels of the 802.3bt. An external MOSFET architecture allows users to size the MOSFET to their application’s requirements; standard LT4295-based implementations routinely select 30 mΩ RDS(ON) MOSFETs.
The LT4295 is offered in industrial and automotive grades, supporting operating temperature ranges from –40° C to 85° C and –40° C to 125° C, respectively. The controller is list priced from $2.75 each in 1,000-piece quantities and available in production quantities.
