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UCC2897A Three Output Synchronization

Jared Becker
Genius 11515 points
Other Parts Discussed in Thread: UCC2897A, PMP7413

Hi team,

Is there a way to synchronize the switching frequency of 3 output rails using the UCC2897A?

The reference I am using is the TI Design PMP7413

Thank you,

Jared

  • 0
    TI__Mastermind 25570 points
    Hello
    Three UCC2897A devices can be synchronised as follows. The SYNC pin is bidirectional and synchronisation is achieved simply by connecting the SYNC pins together. The system of three devices will automatically synchronise to the fastest of the three oscillators. Note that the PMP7413 SYNC output is for demonstration purposes only - the output at TP5 is approximately a square wave running at half the switching frequency of the power train.

    Of course the UCC2897A could be synchronised to an external clock if desired - again just tie all three SYNC pins together and feed them from the clock source.

    The ext sync pulse width should be > 50nS and < (1-Dmax)*Tsync.

    More details on synchronisation are given in Section 8.3.6 of the datasheet.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    TI__Genius 11515 points
    Colin,

    This was really good info, but I was curious if a single UCC2897A could provide 3 output rails that could all be synchronized to the same frequency? I imagine this could be possible depending on the configuration of the transformer, but I am not sure.

    Thanks!
    Jared
  • 0 in reply to Jared Becker
    TI__Mastermind 25570 points
    Hi Jared
    I'm not sure if I understand the question - can you send a sketch ?

    If your question is whether a single UCC2897A can control three outputs independently of each other then the answer is no. Of course you can have multiple windings on the secondary of the transformer and then regulate on one of them, or regulate on a weighted average of all three but there aren't enough degrees of freedom to allow a single controller to regulate all three outputs independently. That is why I suggested using three synchronised UCC2987A controllers.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    TI__Genius 11515 points
    Hi Colin,

    That answers my question, I will let you know if I have any additional questions.

    Thanks for your help!
    Jared