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PMP5236: redundant power question and the PD alternative

Sam Ting
Expert 3660 points
Part Number: PMP5236
Other Parts Discussed in Thread: TPS23754, TPS23756, TPS2372, PMP20859

Hi Team,

My customer would follow the PMP5236 design, but has two questions below,
1. Can this design operate normally to support 12V/2A output power if one of the source is failed or unplugged?
2. The PD in this design is TPS23754, is it okay to apply TPS23756 without any changes? As I know, the only difference is start-up voltage.

Best regards,
Sam Ting

  • 0
    TI__Mastermind 41800 points

    Hi Sam,

    Nice to hear from you!

    1. Short answer is yes; this is a current sharing application; if the power level is within the rating of the power supply (in this case 12V/2A) then it will have inherent smooth transition between the PoE inputs when one is removed.

    Note however, you still must meet the inrush delay spec per the IEEE standard when either one of the PoE inputs first gets inputted. This means the load must wait 80ms before going into higher (2A). Also you must still meet the MPS spec of at least 0.5W to maintain the PSE connection when you're in light load conditions.

    If current sharing is not a hard requirement and smooth transition is the main goal of your design, I recommend looking at PMP20859 which does smooth transition and takes into account of the inrush delay spec and MPS spec of the standard by using the TPS2372's inrush delay and autoMPS features. It's test report shows the transitions when either PoE input or adapter inputs are plugged and unplugged.

    2. Yes I have seen designs that replace TPS23754 with the TPS23756. You're right the only difference is what voltage it starts up. It's possible but be sure you check startup within your input voltage and output current operating ranges to verify the solution.

    Regards,

    Darwin

  • 0 in reply to Darwin Fernandez
    TI__Expert 3660 points

    Hi Darwin,

    Thanks for your clear comments and good support!

    Best regards,

    Sam Ting

  • 0 in reply to Darwin Fernandez
    TI__Expert 3660 points
    Hi Darwin,

    My customer would adopt the configuration as PMP5236 and wants to know we should apply UCC29002D/1 (in BOM) or UCC29002D? and what's the difference? Thanks!

    Best regards,
    Sam Ting
  • 0 in reply to Sam Ting
    TI__Genius 9230 points
    Hi Sam,

    They are the same part, just different markings.
    www.ti.com/.../search

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer