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TPS40057, should sync function be used at parallel operation?

lee 84680
Intellectual 320 points
Other Parts Discussed in Thread: TPS40057

Hi, I am using TPS40057 for POL design, this POL has a parallel feature so I added additional circuit for it.

The POL works good individually, but output currents show 180 degree out of phase(like two sine waves are 180 degree out of phase)  during parallel operation.(run two POLs together)

However this problem is gone if an external clock is being used to the sync pins for synchronization.

So should we use sync pin function of TPS40057 for parallel(load share) application?

Thanks.

 

  • 0
    TI__Guru**** 191445 points

    Can you post your schematic? And any waveforms that demonstrate your concern?  Also, TPS40057 is external FET controller.  Why not size one converter to handle the entire load?

  • 0 in reply to JohnTucker
    Intellectual 320 points

    Hi John,

    I put a similar picture instead of the schematic as below since I am replying from my home.

    The reason which I have to add parallel function is a standard product design under small PWB size. So users can decide to use one POL or two POLs for high power.

    I may have to add the condition of sync pin usual for parallel operation  in datasheet, but I want to know why we have to use sync pin of the IC for parallel operation.

    Otherwise the output currents shows as below. Thanks.

     

  • 0 in reply to lee 84680
    TI__Guru**** 191445 points

    I understand about 180 degree out of phase.  But i wonder how you are implementing parallel operation.  TPS40057 is voltage mode control, so usually it is not practical to implement parallel operation.