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UCC28950: Dahasheet explanation UCC28950

lev nemets1
Intellectual 475 points
Part Number: UCC28950

Hello,

Could you, please, explain formula 154 in datasheet. What is " ",and " "?  Where did you get a value for these parameters before you used it in formula 154.

Is   the same as  ?

Also datasheet says that Rab and Rcd have to be more than 13k, but what happen if its value is less than 13k. Simulation shows that it is ok.

Thanks

  • 0
    Intellectual 475 points

     What is "CS",and "Ka "

    Is Tcdset is the same as tcdset as in formula 153?

  • 0
    TI__Mastermind 25570 points

    Hello Lev

    Unfortunately the content inside the quotation marks " " in your post was lost - I'm going to guess at it but please let me know if I haven't answered your question.

    The formula is an empirical one that should correspond to the graphs in Fig 29 and Fig 30 - if you put in 13k and 90k respectively.

    RCD is the resistor at the DELCD pin - see Fig 48

    CS is the peak voltage of the current sense signal

    KA is a parameter defined in eq 5   - it relates to the potential divider at the ADEL pin.  ( RA/(RA+RAHI) )

    The lower limit of 13k was set at the time that the part was designed by considering the long term reliability of the IC. The controller will operate outside these limits in a Laboratory environment but TI will not recommend doing this in a production design. It is possible to adjust the delays using the ADEL and ADELEF pins as described in the data sheet.

    Regards

    Colin