TPS2379DDAR

The integrated circuit mentioned in the PDF that contains all the features needed to implement an IEEE802.3at type-2 powered device is the TPS2379.

The purpose of the external pass transistor in the TPS2379 for higher-power applications is to share the total load current with the internal hotswap MOSFET, enabling the TPS2379 to handle powers significantly above the IEEE 802.3at, type 2 levels. This allows for boosting the TPS2379 hotswap MOSFET operating current limit, which is achieved by adding an external pass MOSFET. The external pass transistor is enabled by the GATE pin after the internal hotswap MOSFET inrush is complete, and it helps in limiting the current and balancing the load currents between the external and internal pass MOSFETs. Further details on this can be found in the application report "Implementing a 60-W, End-to-End PoE System"