9.2.1.2 Magnetics

A high-power PoE system places additional burden on power extraction from data pairs. Data transmission properties must be maintained while carrying higher current and withstanding higher difference current between the conductors in a pair. This difference current is the result of unbalanced resistances between the conductors of a pair (see IEEE 802.3af annex 33E).

Either a higher current center-tapped transformer as shown in Figure 13, or the addition of a center-tapped inductor, can be implemented. Proper termination is required around the transformer to provide correct impedance matching and to avoid radiated and conducted emissions.