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TPS23750: Keeping the PSE power supply

tateo yamashiro
Guru 10890 points
Part Number: TPS23750

Hi,

We got a question from the customer about TPS23750.
Could you help us?

[Question]
They refer to section 3.6 of SLVA306A for ORing solution. When an adapter is removed, they want to prevent the interruption of power supply. So they have a question.

- When both adapter and PSE are connected to PD, does the PSE complete its detection, classification, and start-up sequence? In other words, when ADP is removed, is there any possibility to occur the power interruption?

Best Regards,
tateo

  • 0
    TI__Mastermind 40120 points
    Hi Tateo,

    When the adapter is plugged in first, the adapter voltage will be present on the PD front end. When the PSE is connected, it won't be able to connect. When the adapter is removed, since the PSE do detection classification, there will be power interruption.
  • 0 in reply to Darwin Fernandez
    Guru 10890 points

    Hi, Thank you for your reply.

    I think Dvdd present to prevent the phenomenon that you mentioned. Therefore I assume the PSE can complete its detection. Is this my understanding correct?

    According to app note, when used in option 2, there is a short power interruption. But if used in option 3, there is only small delay before PoE converter goes from inactive to supplying power. So I assume if used option 3, there is not power interruption. Is this my understanding correct?

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Mastermind 40120 points

    Hi Tateo,

    Yes option 3 diode ORing on the secondary is the simplest solution. We typically see this in 12V applications. The key is that the PoE voltage is less than the adapter voltage (including tolerance).

    Option 2 ORing even with the diode between VDD and VDD1 still gets complicated for smooth transition mainly due to the voltage at the PD (from different length cables) can be different than the adapter voltage.