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 http://www.nomad.ee/micros/mc34063a/index.shtml,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) the values in the schematic are for a 25v input to 5v output (500mA) 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... I aslo added a switch to allow me or any other use to swtch the microcontroller on and off. http://www.alldatasheet.com/view.jsp?Searchword=MC34063 If it helps anyone, I am using the Pic24fj256ga110 from microchip ( the switching regulator will be connected to this u-controller). http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en531069 Thank you in advance for any advice and help.