I am thinking of using an 8-order LPF switched capacitor: MAX7405 http://www.kynix.com/Detail/407475/MAX7405ESA%2B.html
The cut-off frequency should be set by simply connecting an external oscillator capacitor, Cosc.
I would like to design a 50Hz cut-off frequency but I have doubts on my calculation for the given formula in the datasheet.
Since I want to have a 50Hz
fC, I needs the
fCLK to be 5000Hz
From the given equation:
fOSC(kHz) = (K * 10^3) / Cosc; Cos in pF , K = 34 for max7405
5000(k) = (34 * 10^3) / ( C * 1pF)
5000 = 34 / ( C * 1pF)
C = 34 / 5nF
C = 6800M
By using the above equation, I calculated an extreme large capacitor with Mega value which is not reasonable.
Am I calculating it in the right way?