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Full Version: Which is the right tool to use
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Hello guys

I am confronted with a problem I can solve just by using the prime as an ordinary calculator but I could imagine that there is a built-in tool for doing the job.
Maybe a user program would be an option, but I am so busy at work atm that messing around with the programming does not seem to be a good idea.

The problem is that:

I need to design several switching supplies with different feedback voltages and different bias currents on them. What I want to solve is: (R1+R2)/R2 == U0/Ufb.

U0 is given
Ufb is given
R2 is given by myself and in the range of, say, 120k..270k. Pre-defining R2 values so that they match E24 would be sugar on top.

Is there built-in feature that I can quickly use?

You can use the spreadsheet application. See the attached simple example where U0 and Ufb are named cells, column C contains the R2 predefined values (you can put what you want here) and column D has the column-wide formula: "=C:C*((U0/Ufb)-1)"
Just enter the values of U0 and Ufb you want to design for and you’ll get in columns C and D the pairs of R2/R1 values.
You can customize this spreadsheet as you need.
Thank you for the suggestion!
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