[SOLVED] LMF100 as a variable fitler - trying to smooth the output

[atferrari]

A square wave ranging from 10 to 1000 Hz is filtered with an LMF100 (switched capacitors filter - bandpass) to obtain a sine wave.

Using fCLK/f0 = 100:1, fCLK goes from 1000 Hz to 100 KHz.

Basically it works, but, to smooth the step-like output, I intend to use a single lowpass RC cell as the datasheet reccomends.

Problem is that an RC filter able to stop the 1000 Hz (fCLK) at the lower range is affecting my output at the upper end (1000 Hz as well).

I feel I am going in circles loosing the advantages of a continuously variable filter as implemented.

Still in square one and perplex, wondering how the pros do it.

BTW my idea is not to start switching things along the range. Oh no!

Ideas anyone?

 

[atferrari]

Solved.

At two convenient points I switch a second and a third capacitor in parallel with a permanent one. It runs smoohly along the whole range.