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Original question:

TPS23754: Could you kindly help to check the Schematic?

TPS23754: The power powered off.

Lian Wu
Genius 5250 points
Part Number: TPS23754

Dears:

There will happen power off and the waveform as follows:

Verifying the 25W load ( using the cement resistor), running for a period of time (such as a few hours), there is no power failure problem, during this period may be overloaded. This time take off the load, and the device is then powered normally. In this case, the device has only the device (5W), but the problem happened.

1. PSE side waveform:

  • 0
    TI__Expert 5615 points
    Lian,

    I have assigned this thread to PD Application Engineer Tom Amlee. As it is the weekend, his response will be delayed by ~12 hours.

    Thank you for your local support of PoE products from Texas Instruments,
  • 0 in reply to Thomas Lewis
    TI__Genius 9230 points

    Hi Luck,

    To clarify: your PSE is removing power to your PD when you startup with a 25W load attached. When a load is not attached, you are able to successfully startup with a PSE.

    Do I have this correct?

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer

  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points
    HI Luck,

    In section 7.4.1.5 of the TPS23754 datasheet, it says "the application circuits must assure that their power draw does not cause the PD to exceed the current/time limitation." You will need to make sure the load is not attached until after this inrush period.

    By startup up with a load attached, the inrush current is flowing in to the power stage instead of charging the bulk cap. If the bulk cap is not charged, PD stays in inrush for longer until it reaches thermal limit, shuts down, & tries again.

    Regards,
    Tom Amlee
    PoE PD Apps Engineer
  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points

    Hi Luck, 

    If you are still working this issue, feel free to reply. If you have found resolution to your question, please click the green "resolved" button.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer