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TPS23751: Detect Active and Passive PSE

Part Number: TPS23751

Hi Expert, 

Do we have any way to detect active or passive PSE or other companion part to do it?

Thanks.

Allan

  • Hello Allan,

    My understanding of active vs passive PSE is this: active PSE's follow the IEEE 802.3 af, at or bt standards. Passive PSEs do not follow any standard, and does not negotiate power. Passive PoE is "Always On"

    You could use the T2P pin, since it will not activate if an .at or .bt handshake is not detected. But this assumes the PSE's will not be .at.

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • Hi Michael,

    "assumes the PSE's will not be .at." I am a little bit confused. Do you mean ".af", correct?

    Thanks,

    Allan

  • Yes, sorry I meant the PSE's can't be .af

    Thanks!

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • hi, michael

    we know T2P, and implemented.

    But the question is there any way to seperate .af and the passive(non-standard)? Because .3af won't provide sufficent power budget, and will lead to the system unstable.

    thanks

    Jerry

  • Hello Jerry,


    There is no way outright to do it on the TPS23751. 
    If you were willing to switch devices to a device with PPD, then you could do it. 

    Alternatively, if the Active PSEs were only on one pair set (ex. 1&2, and 3&6) and the Passive PSEs were on a different pairset (ex. 4&5, and 7&8). Then you could tell the difference, but you would have to force this configuration. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • as i checked, the PPD is to detect the low voltage of power source but our application is 48V... Anyway , thanks for the answer.