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TPS23754: pls help take a look at this problem?

xiaofu wen
Expert 2365 points
Part Number: TPS23754

We need to use TPS23754 to make a POE and Adapter (24V, Adapter priority) power supply, and ensure that the POE can continue to power supply when the Adapter power off. We are not sure whether PSE side has the monitor function. We need to add a regulator and a resistor after PD rectification to maintain at least 10mA current.

  • 0
    TI__Genius 16191 points

    Hi Xiaofu,

    Thanks for reaching out to us!

    You are correct that the PSE side has a current sensor and needs to receive a maintain power signature (MPS) from the PD. It means the PD needs to act as a load all the time to avoid the PSE turns off the port. For AT standard, the PD could be either pulse (duty cycle > ~25%) or dc current with amplitude > 10 mA at that condition.

    In your picture, it is a DC load for MPS. It needs to meet V(adapter) - V(all oring diodes forward drop) - V (zener) > 10 mA x R. Besides, APD needs to be disabled for a hitless adapter->PoE transition.

    Best regards,

    Diang