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TPS23754: Classification PoE+

user5884477
Prodigy 110 points
Part Number: TPS23754

Hi, 

As attached is my design using the TPS23754PWPR.

It's working well if I use an injector for IEEE 802.3af standard, like p/n TL-POE150S.

But it's not working well if I use an injector for IEEE 802.3at standard, like p/n DPE-301GI.

You can see what I scope on D11. It Looks like the converter try to start, but just cant.

I sometime see D13 flashing.

I tried to add capacitor (several uF) at C97, C98 and D14.

I tried different values for frequency switching, blanking and current sensing resistor (R84, R86 and R98).

Would you have any suggestions ?

Thanks

  • 0
    TI__Mastermind 21320 points

    Hello,

    It looks like the converter does detection, class, turns on for 400ms, then turns off and repeats. It appears that it can properly negotiate power, but the maintain power signature (MPS) is not met. Try increasing the load, or adding a resistance between VDD_RTN. 

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments