WHSG50011PG Gigabit PoE+ LAN Transformer

Because open-circuit inductance is measured under a DC bias, and the bias has to sit near the real supply operating point for the figure to mean anything.

The WHSG50011PG states 350 µH Min at 14 mA bias, while the non-PoE and 802.3af parts in the same family state the same figure at 8 mA. When comparing PoE parts, read the bias condition alongside the inductance — comparing the numbers alone compares two different operating conditions. Bias conditions vary across the 100/1000 BASE-T range.

In three places: the PoE class moves from 802.3af / 350 mA to 802.3at / 720 mA; the inductance bias condition moves from 8 mA to 14 mA; and insertion and return loss change from fixed values per band up to 100 MHz to functions of frequency up to 125 MHz.

The WHSG50011PG also puts its common-mode choke on the pin 1–25 side where the other three put it on the pin 26–50 side. Package, pin net names and temperature grade match, so the PCB does not change, but EMC has to be re-measured after a swap. The 802.3af part sits on the same land pattern.

Not as an 802.3bt part. The WHSG50011PG datasheet states 720 mA current capability, suitable for IEEE 802.3at.

Type 3 and Type 4 under 802.3bt draw more current than the 802.3at class, and the figure cannot be extrapolated upward. A port running 802.3bt needs a device rated for that class; tell us the per-port current you are targeting and VOOHU will confirm the applicable scope against the current controlled document. Higher-current parts are listed in the 100/1000 BASE-T range.