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TPS23754EVM-383: TPS23754 debug

Part Number: TPS23754EVM-383

Hi Team,

I am facing an issue with TPS23754. When i turning device with PoE adapter, PoE adapter LED is keep on blinking. When i probe at rectifier, 55V pulses are coming. Please have a look on schematic attached.

8 Replies

  • Hi Saurabh,

    Is there a load on the output of your converter? If not, can you try adding a load less than 13W (but not no load)? Thanks!

  • In reply to Darwin Fernandez:

    Hi Darwin,

    Load is there.
  • In reply to Saurabh Gupta:

    Hi Saurabh,

    I don't see an adapter connector on the schematic, where is the voltage being applied? Also, is the adapter voltage able to provide the power from the load (it could be the adapter is hitting its current limit)?

  • In reply to Darwin Fernandez:

    Hi Darwin,

    Power is applied at RJ45 from PoE adapter whose rating is 802.3at. Please find the schematic of whole PD controller with RJ45 and rectifiers.SCH_501-1-00485_B1.1.pdf

  • In reply to Saurabh Gupta:

    Hi Darwin,

    This is very critical issue to me. Please help me on this.

  • In reply to Saurabh Gupta:

    Hi Saurabh,

    The fact that the midspan is turning on to 55V means that it is successfully doing detection. The reason I ask about the load is because there must be a minimum of 10mA to keep the PSE connected. In addition, the load can't exceed 13W for the first 80ms the PSE turns on to 55V otherwise it will turn off. Another reason for the blinking is that the PSE is hitting it's current limit from overloading. For that we will need to see it's port voltage and current waveforms.

  • In reply to Darwin Fernandez:

    Hi Darwin,

    Thanks for your reply.

    I have connected a load of 5W, but same blinking is happening at poe out.

  • In reply to Saurabh Gupta:

    Thanks for verifying Saurabh, can you take the VDD-VSS and input current waveform during detection, class, and startup? It should look similar to Figure 22 of the datasheet (if the PD and PSE are communicating correctly). Thanks!

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