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TPS2378: Selecting an appropriate 8P8C jack

Part Number: TPS2378

Hi, this is my first post here. I have some experience designing around Arduinos and ESP32's, but this is my first design with PoE and the TPS2378.

Basically, i've been told that jacks with CTs on the "board-side" are useless for PoE, such as this one (P4 and P5):

And instead, they need to be connected like this (R8 & R7):

Is that correct? Having some trouble wrapping my head around this. If so, this means that this HR861153C below is a Mode B-only jack? Since wires 4,5 & 7,8 go to the rectifiers, and only "board-side" CTs connect to the rectifiers (Mode A, but board-side?)?

  • Hi Maciej,

    Thanks for reaching out. 

    The PoE power can be transmitted by 2-pairs or 4-pairs. TPS2378 is an AT PD controller, with an AT PSE the power can be sent by pair 12 & pair 36, or pair 45 & pair 78. Looks like data transformer you have only covers pair 12 & pair 36 data. For the power path it should be still work for pair 12 & pair 36, or pair 45 & pair 78. 

    If mode A is used, the middle tap of transformer winding can be used to the DC current out. If mode B is used, the wire 4&5 can be directly shorted, so does wire 7&8. Below is an example of PoE interface can work for both mode A and B. 

    Best regards,

    Diang