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TPS23861: the PD detected and PD classified are ok，power on is mistake

chao wang
Prodigy 50 points
Part Number: TPS23861

In my design，TPS23861 is PSE controller and  default to auto-mode operation（Circuit diagram as follow picture1）。when connect POE device，power on is mistake，the PD detected and PD classified are ok（the Curves as follow picture2 and picture3，blue indicate Vgate，greeen indicate Vsen，yellow  indicate Vdrain）。I think this mistake  is from Protection ，but how to recognize Overcurrent Protection and Overload Protection or Inrush Protection or current-limit protection in auto mode

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    TI__Genius 15685 points

    Hi,

    Thanks for providing all the detailed information. From the waveform, I can tell the TPS23861 is doing what it is supposed to do. In the IEEE802.3at standard,  the PD must present a minimum dc current of 10 mA (or a 10-mA pulsed current for at least 75ms followed by an optional MPS dropout for no longer than 250ms) to keep the PSE port on(it is called MPS: maintain power signature), otherwise the PD will lose its power. 

    From the waveform above, it looks like the PD didn't present a valid MPS, so the PSE removed the power after ~360ms. Please check with a standard compliant PD with your TPS23861 board and it should be no problem. Thanks.

    Best regards,

    Penny