I'm looking at pcb-mount Ethernet ports like these:
I'm seeing a few different configurations of the magnetics within the ports. On a single Wurth data sheet, there are 4:
Schematic 2 is the part we currently use, but is going obsolete. I found potential replacements which look more like Schematic 1.
What is the difference? Are there benefits to the different designs?
Best Answer
Schematic 1 offers direct connection to the center tap of the exterior port windings, and is suitable for PoE connection (which may either draw power, or supply power, over twisted pair). Schematics 2 and 4 do not have low-resistance connection suitable for PoE. Schematic #3 does technically have the ability to connect to PoE, but only through an inductor (which may saturate).
Modern designs would usually allow bidirectional use of the four lanes, and #2 does not. It is not surprising that it may become obsolete, in favor of #4.