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TPS23756: passive and standard hardware schematic

Part Number: TPS23756

Hi Team,

is the  passive and standard input TPS23756 hardware schematic totally the same? with no software control?

thanks!

  • Hi Bonnie,

    Could you clarify:

    By "passive input" are you referring to OR-ing before the PD controller? (fig. 34 on the TPS23756 datasheet)

    By "standard input", are you referring to primary side OR-ing after the PD controller? (referred to as "option 2" in our adapter OR-ing app note: www.ti.com/.../slva306a.pdf)

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer
  • Hello Amlee,

    let me clarify the question.

    Customer is looking for a design could support standard PSE source and adapter power source input on the same RJ45 port in 2-pair or 4-pair source.

    For adapter source, the voltage would be 24V and 48V.

    And also, csutomer also need indication to tell user the source type as standard or adapter.

    They want to keep the same schematic to support all of requirement above.

    could you please advise or provide the function block how to achieve it?

    BR,

    Jason

  • Hi Jason,

    I will discuss more with the team on Monday & get back to you next week.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer

  • Hi Jason,

    I have sent you an email, offline.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer
  • Hi Bonnie,

    To answer your original question: you would need to design a voltage divider on the PPD pin such that the voltage needed to turn on the hotswap FET is just above the classification range (>21V,) & meet's your adapter's minimum voltage range. There would not be significant change to what is implemented on TPS23756EVM aside from adding the additional diode bridge for 4-pair.

    Jason, regarding the indication of which kind of input is present, there are not many options considering that PPD going high or a type 2 PSE being connected will pull T2P low. They may have to go with a software solution, but we can discuss more, offline.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer