I'm researching the design of a PoE splitter. I understand the actual 802.3at portion of things, and have some confidence in being able to get the 48 VDC out (TPS2378).

The question I have is... I've got the center tapped 1:1 transformers on the incoming pairs. That's fine. But what do I do with the secondaries of the transformers such that I can just connect up to an RJ45 intended to be the jack for the target device?

Is it just simply wiring the secondaries to the output jack?

  • \$\begingroup\$ Have you got centre taps on incoming and outgoing magnetics? \$\endgroup\$
    – Andy aka
    Mar 5, 2016 at 9:32
  • \$\begingroup\$ Yes. That's required to pull the power off. \$\endgroup\$
    – nsayer
    Mar 5, 2016 at 15:50
  • \$\begingroup\$ Wait. "Outgoing magnetics"? \$\endgroup\$
    – nsayer
    Mar 5, 2016 at 16:12

1 Answer 1


This schematic appears to answer the question: the output of the secondary of the magnetics appears to go directly to the outgoing RJ45 jack.

  • \$\begingroup\$ If that's solved it don't forget to mark your answer as accepted, otherwise it'll keep getting bumped as unanswered. \$\endgroup\$
    – PeterJ
    Mar 8, 2016 at 11:21
  • \$\begingroup\$ Since I answered my own question, there was a waiting period. \$\endgroup\$
    – nsayer
    Mar 8, 2016 at 19:25

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