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TPS23754: TPS23754 TEST SIFOS ISSUE

user5157625
Prodigy 120 points
Part Number: TPS23754

HI  SIR,

I has designed the schematic now, but the test sifos did not pass, please help confirm what the problem？The following is the details:TPS23754 TEST SIFOS ISSUE.zip

  • 0
    TI__Mastermind 41790 points

    Hi User,

    Do you expect your TPS23754 to always connect to a Type 2 PSE?

    The SIFOS failure is saying that when a Type 1 PSE (15W) is connected to your PD design, the output power of your design is 25W. This means the Type 1 PSE will fail. A Type 2 PD should adjust it's output power to 13W if a Type 1 PSE is connected to it.

    This is the use of T2P on the TPS23754. In addition, below is an FAQ that discusses T2P and its use in more detail.

     

  • 0 in reply to Darwin Fernandez
    Prodigy 120 points

    hi   darwin,

       I can't confirm TPS23754 to always connect to a Type 2 PSE, beacuse  I tested sifos through a third-party testing organization.and my product need fulfill the standard for "AT".and then i have a qusetion :

      I made the schematic according to the reference design. There are two different layouts,the AZ709-DAP is fail ，but AZ710-DAP is pass.Such as attachment.

    In addition to T2P causing sifos failure, is there any other reason? Looking forward to your reply.thanks.

     

  • 0 in reply to user5157625
    TI__Mastermind 41790 points

    Hi User,

    Even if both boards use the same PoE power design, it depends on the actual output load. For example, even if one board can operate up to 25W but the condition during the SIFOS testing is operating at 13W or less, that board will pass SIFOS (even the Type 1 test on SIFOS). So probably one board (passing) is operating this way while the second board (failing) is always operating at 25W.