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MC33063A: Buck Converter Design Values

Ayyanar Raja
Prodigy 40 points
Part Number: MC33063A

Tool/software:

Hi Forum Members,

I'm trying to match the Buck converter design values through the Calculator from formula given in Datasheet.

From this calculation I'm trying to find the Frequency behind this CT & L. Considering this reference frequency value, I need verify other design we are using.

The calculator I prepared having issue such that, If I match CT, L is not matching and wise versa. Attaching the Calculator excel file and picture of reference design from Datasheet. Anyone please help to fix the conflict.

MC33063A Step down.xlsx

  • +1
    TI__Guru 65170 points

    Hello Ayyanar Raja,

    Please be aware that this device is not a fixed frequency converter. The frequency changes with the current through the inductor. Especially if the current limit is reached.

    I updated the calculator according the formulas in the datasheet: MC33063A Step down updated.xlsx

    The formula for the timing capacitor needs 40 instead of 0.4.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 40 points

    Hi Brigitte,

    Thanks for the updated file. I have gone through the formula, and it looks fine now.

    Yes, I'm aware that the frequency will change based on the current through the Inductor and Frequency can be controlled by Ct in this IC.