WHD12502G 10/100BASE-TX LAN Transformer

The WHD12502G is the only part in this family with the common-mode choke on the chip side: the signal enters at pins 1–6, passes the choke first and the 1CT:1CT transformer second, then reaches pins 7–12. The others put the transformer first and the choke second.

With the element order changed the common-mode path changes with it, so even where outline and hole positions match, EMC has to be re-verified after a change — the parameter table cannot establish equivalence. Other internal arrangements are listed in the 10/100 BASE-T range.

By the marking on the body: every part carries its own part number plus a YYWW date code, and this one reads WHD12502G.

Several parts in the 10/100 BASE-T range share body size, row spacing and hole diameter exactly and drop into the same holes without resistance, so the marking is the only visible difference. Incoming inspection and the pre-run check should go by the marking; tube quantities differ between parts and can serve as a secondary clue, but not as the sole criterion.

Indoor 100M port equipment where the component temperature stays between 0 °C and +70 °C and the PCB already carries a 12-pin through-hole layout on a 14.00 × 7.70 mm outline with 4.80 mm row spacing.

The WHD12502G has no PoE capability, so the port is powered locally; the body stands 6.00 mm and the part is wave-soldered. Equipment powering up below 0 °C needs the wide-temperature grade, and a board drilled to the 5.00 mm row spacing cannot take this part at all. Both outlines are listed in the 10/100 BASE-T range.