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TPS23861: PSE 12V issue

Patrick Chen
Mastermind 8875 points
Part Number: TPS23861

Hello

            Below is customer topology. 54V_GND has no isolation so directly connect to PSE_RJ45 and RJ45 of POE. So there are 12V supply voltage on RJ45. Is it correct design for below topology? How to prevent t o12V voltage on RJ45 ?  If customer don't change to system design, what will cause any side effect or damage risk by this phenomenon? Thank you. 

BR

Patrick

  • 0
    TI__Genius 15685 points
    Hi Patrick,

    the topology looks correct but I didn't catch your question. Why there's 12V supply on the RJ45 port?

    Thanks,
    Penny
  • 0 in reply to Penny Xu
    Mastermind 8875 points
    Hello Penny

    54V adapter GND is connected with RJ45 GND. So while input 54V adapter, there is 54V supply voltage on RJ-45. So TPS23861 has no any function.

    While 54V adapter plug in, there is 54V supply voltage on RS45 immediately, has any security issue for it? Could the design pass safety? Thank you.


    BR
    Patrick
  • 0 in reply to Patrick Chen
    TI__Genius 15685 points
    Hi Patrick,

    Please check TPS23861EVM-612 schematic. The RJ45's ground is the same as the VPWR ground. But there's no voltage on the RJ45 port. the voltage on the port is depending on the voltage between pair 12 and 36, or pair 45 and 78. So only when you turn on the PSE port, 54V will be on the PSE port and power can be delivered to the PD. the 54V GND will not be connected to PD. the only connection between PSE and PD port is the cat 5 cable which has 4 pairs: pair 12, 36, 45,78. Thanks.

    Best regards,
    Penny