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UCC256404: ucc25640x datasheet typo?

robin gangopadhya18
Mastermind 6296 points
Part Number: UCC256404


Hello:

Would you pl check into this para in the UCC25640X datasheet

One would think the "gain increasing " with DECREASING freq " will be an appropriate statement here.

Maybe it was pointed out elsewhere in the Forum...

-r

  • 0
    TI__Genius 16155 points

    HI Robin,

    This paragraph is correct. In the ZCS region (highlighted below) , gain increases as frequency increases. 

    Regards

    Manikanta P

  • 0 in reply to Manikanta Pallantla
    Mastermind 6296 points

    THNX for the prompt reply.

    In the sense you have highlighted, yes, before the peak, starting from low freq , gain increases.

    Generally though, it seems to me, in line with "others" writing about "capacitive ZCS avoidance" schemes, they mean from steady operation, as load increases, operating freq deviates from resonance, moving left of the FR.

    Operating frq might enter a zone BEFORE THE PEAK GAIN, WHERE ZCS renders feedback +.

    So  circuits have to sense that & prevent entering this "zone' well before the gain peak.

    Is this understanding "wrong", you think?

    r

  • +1 in reply to robin gangopadhya18
    TI__Genius 16155 points

    Hi Robin.

    your understanding is correct.

    The paragraph in the datasheet strictly referring to the ZCS region where gain increases as frequency increases.

    In addition with the ZCS region, there is a  ZVS region below resonant frequency where gain reduces as frequency increases. 

    UCC25640x detects the ZCS by sensing the current polarity during turn off. After it detects the ZCS, controller immediately increases the switching frequency.

    Regards

    Manikanta P