Using a Step-down switching regulator, how can I convert 12v to 3.3v ?

Hello, I am working on a project. And part of it concerns the switching regulator.

I am using the MC34063 from OnSemiconductors.

I plan to use it as a step down converter, 12v to 3.3v with a 200mA output current, so I can power up a microcontroller and other IC's but I have a hard time finding out some of the component values...

I tried using the calculator from the following website <a href="https://www.nomad.ee/micros/mc34063a/index.shtml" target="_blank" rel="nofollow noopener noreferrer">www.nomad.ee</a>,but there are certain values such as the voltage ripple and Minimun frequencies which confuse me a little bit.

I am using the following schematic design (this can be seen in their datasheet under stepdown converter)

<a href="https://www.alldatasheet.com/view.jsp?Searchword=MC34063" target="_blank" rel="nofollow noopener noreferrer">MC34063 Datasheet, PDF - Alldatasheet</a>

I tried adding different values which I calculated from the given formulas in the datasheet and even tried using the calculator, but when I simulated these, it did not work...😳


If it helps anyone, I am using the Pic24fj256ga110 from microchip ( the switching regulator will be connected to this u-controller).

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Thank you in advance for any advice and help.😛