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MC33063A: calculating Switching frequency

Electro_crazy
Intellectual 525 points
Part Number: MC33063A

Hello,

MCP33063 has a timing capacitor to change the switching frequency (Pin 3). For buck converter, the timing capacitor value in the example is 470pF (in section 9.2.3).

How can I calculate the value of switching frequency for 470pF?

Thanks

  • 0
    TI__Guru* 78270 points
    Hi Jain,

    Thank you for your interest. I cannot easily copy and paste the datasheet equations here, so let me describe the process.

    There is an equation governing CT and ton. When you chose 470pF, you can calculate your t_on.

    There is another equation determines t_off and t_on ratio. You will get t_off from that equation.

    Then the frequency is 1 /(t_on + t_off).

    Hope this helps.

    Best Regards,
    Youhao Xi, Applications Engineering.