A project involving high-power radios powered by PoE prompted me to look into the maximum power you can get from PoE.
IEEE 802.3af PoE – 15.4W max power
IEEE 802.3at PoE+ – 25.5W max power
Both types of PoE can be Mode A or Mode B.
Mode A – Power delivered on TX/RX pairs
Mode B – Power delivered on spare pairs
TI has a circuit to run Mode A and B simultaneously, resulting in a maximum power of 51W. The implementation is tricky because it must balance the current so that neither Mode A or B lines exceed the maximum current.
I would love to hear from someone who has implemented 51W PoE or used other cheats to get > 25.5W over Ethernt.