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TPS23754: Sifos test fail

Tommy Tzeng
Genius 5780 points
Part Number: TPS23754

Tool/software:

Hi Sir,

as attached the schematic, and Sifos PDA-602 test TPS23754,

the test fail item is as below, could help us confirm any suggestion for this schematic or what need to be modify? thnaks for your help and learn from you.

TPS23754 schematic.docx

  • 0
    Genius 5780 points

    Hi Sir,

    as attached is Sifos_PDA600 test result report for you reference.

    pda600_trace_report-46.xlsm

  • 0 in reply to Tommy Tzeng
    TI__Mastermind 37121 points

    Hi Tommy,

    Thanks for your information. From your current trace the issue could be related to the DC/DC turn on current is too high. Could you try the below 3 actions and see if it can get solved/improved. 

    1. You can further increase R36 or PC4/PC5 to increase the soft-start RC timing. You can also try to mount R39, which allows more current follow into U19 and make U19 more stable. 

    2. Other than the shown caps, do you also have other caps at 24V bus? You could consider reducing the capacitance to reduce the DC/DC start up inrush current. For 25.5W and 24V, you may only need 47uF electrolytic cap.

    3. By increasing the input cap from 22uF to 47uF, you could have more current come from PC24. So PSE current can be lower.  

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Genius 5780 points

    Hi Diang,

    thank for your help , we have solve some issue, but we would like to adjust the delay during this period, is that possible? as attached.

    PTX-請益.pptx

  • 0 in reply to Tommy Tzeng
    TI__Mastermind 37121 points

    Hi Tommy,

    Thanks for your reply. I will be in time bank recently. I will try to get back to you in the next week.

    Best regards,

    Diang

  • +1 in reply to Diang Xing
    TI__Mastermind 37121 points

    Hi Tommy,

    Thanks for your patience! Which delay time do you want to adjust?

    If you want to increase the inrush delay, you can add a 47uF electrolytic cap between VC and RTN.

    If you want to increase the soft start delay, you can further increase R36 or PC4/PC5 to increase the soft-start RC timing (2x to 10x can be tried).

    Best regards,

    Diang