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UCC28700: SLUC408B spreadsheet

Boris Baskevitch
Prodigy 30 points
Part Number: UCC28700

Hello,

I'm using the SLUC408B spreadsheet to calculate the BoM parameters for an isolated flyback DCDC based on UCC28700.

In this XL sheet, on line 121 we Estimate the FET switching losses with the following formulae:

=(Vfly-(Vout+Vdg)*NpNs)*Ippk*C116*fmax/2

Shouldn't it be

=(Vfly+(Vout+Vdg)*NpNs)*Ippk*C116*fmax/2  ?

And another point: I don't have any Fusable Resistor in my design, so I would like to put zero in line 80 but the spreasheet cell is locked. Is it possible to unlock it ?

Also the Input Ripple is locked (line 62). I would like to change it as I use a DC input for this design.

... and the maximum drain voltage of the FET (line 113) as I use a higher voltage FET

Thank you

  • 0
    TI__Expert 7395 points

    Boris,

    Thanks for your interest in TI here. I've contacted an applications engineer to answer your questions. You should hear back soon.

    Regards

    John

  • 0 in reply to John Stevens
    TI__Expert 7395 points
    Boris,

    Most of these are locked and simplified for most customers to make some common assumptions to make it easier for you as a user. You sound like a more experienced user who prefers to be in control of each detail on the design. :)

    I believe Bernard Keogh contacted you through email on this on how to unlock and edit the calculator. Do you have further questions on this or have we resolved your questions?