I want to add a filter between my AVR and the analog circuits. But I do not know what to use. I want it to be small and cheap. Small is most important. The filter should stop the high frequency from the AVR to reach the analog parts.
This is my options so far:
- Only resistors, maybe 1 k. (higher will decrease signal speed). The resistor should decrease the energy of the signal noise but without capacitor, will it have any effect?
- Resistor + capacitor = low pass filter.
- Multilayer chip bead. This is a wide band inductor.
- Ferrite bead array. Very easy to use as it fit the port pins well. Smallest. But how much would the ferrite do by itself? Should I add capacitors also?
I understand that there is a typical answer to this: "It depends". (On how much filter I need). But some advice would be great from what experience you might have. I will use separate ground planes and a very well filtered power supply.