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TPS2372-4EVM-006: Allocated Power Truth Table issue

Dr. Alexander W. Lenhardt
Prodigy 130 points

Part Number: TPS2372-4EVM-006

Tool/software:

Hello TI team.

Recently I found and issue with the TPS2372-4 evaluation board.

If connected to a PoE++ injector of type POE-171A-95 or POE-171A-60 (manufactuer PLANET, see image attached) I will get unexpected behaviour of TPL, TPH and BT\.

The board is going to pull TPL and TPH low, BT\ stays high.

I tested it with CLSA set to "Class 4",. CLSB set to "Class 6" or "Class 8", AUTOCLS on or off, INRUSHDLY disabled and MPS_DUTY set to 53.4k.

In my eyes it is an undocumented state in the Allocated Power Truth table of page 15-16 in the datasheet.

It's probably telling that only two CAT cable pair is used for power transmission, not all 4.

But LOW/LOW for TPL and TPH is "invalid" anyway.....

I'm pretty confused about that behavior and don't know how to interpret it.

The TPS2372-4 evaluation board is working like expected on a IEEE820.3bt switch.

An evaluation board with STs PM8805 is working like expected with the injectors above.

Could you help me with that?

Thanks for that in advance.

Best regards,

Dr. Alexander W. Lenhardt

  • 0
    TI__Genius 14575 points

    Hi,

    We have received your question. TI US is closed for the Thanksgiving holiday until Monday 12/02. Please expect delayed responses. Our device experts will respond when TI US is back in office.

    Thank You

  • 0 in reply to Alex Liu
    TI__Mastermind 37111 points

    Hi Dr. Alexander,

    Really thanks for your patience. PoE team has multiple leaves and travels at the end of 2024.

    I am wondering if you can measure the TPS2372-4EVM's VDD-VSS. You should see a long classification finger at the 1st (and TPS2372-4 could be based on the 1st finger to tell if it is BT or not). If you did not see this long finger at 1st one, then the PSE may not be fully configured as BT.  

     

    Best regards,

    Diang