I'm using a MAGJACK GIG PDJACK 1X1 CLASS 4 (Molex # 0857914020 - Link: https://www.digikey.com/products/en?keywords=WM9656-ND) to run POE on a 100MBit network connection. I thought this was a nice part since it includes all the POE negotiation systems and magnetics within a single component. The Magjack is then wired into a DP83848CVVX PHY. As this is only 100MBit, that leaves two center taps and wiring pairs unused in the design. Does it matter how the unused pair of magnetics out of the magjack are used? Do I simply leave them unconnected and floating, or do I need to tie the center taps to VCC/Gnd like the other centers?

I'm having issues with the DP83848 blowing out its transmit pair when connecting/disconnecting the ethernet cable too many times (20-30) and am trying to narrow down where things may have gone wrong, and this is one item I cannot find any information on. The TX/RX pairs are wired to a SLVU2.8-4A1 TVS after they leave the magjack, and while this has improved its viability, she still seems to pop after a while.


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