Power Over Ethernet Interoperability Guide

Auxiliary Power Option A (Front Aux or FAUX Pin Method)

The behavior and the requirements depend on the following cases.

V_AUX within PoE Range

In the following discussion, pay close attention to Fig. 14.2. In general, this method is said to support only V_AUX between 42 and 57 V. But there are ways around that restriction as discussed here.

FIGURE 14.2   Front Aux method in more detail.

It is clear that if V_PSE is present (i.e., between 44 and 57 V), V_AUX needs to be greater than V_PSE for the OR-ing diode D1 in Fig. 14.2 to conduct. Therefore ...