I have few questions that I couldn't get by myself:
- Capacitors C26 and C25 are tantalum capacitors(used before ADC supply pin), they are 1 uF, but on the other hand capacitors C42 and C41 are 2.2 uF and are cheap ceramic caps(they are used for internal voltage regulator). The question is - why they use tantalum capacitors before ADC? Can I plug ceramic capacitors there or aluminium electrolytic? Tantalum are expensive and many people say unreliable, basically on any forum people say something like "stay away from tantalum caps". What are implications of using ceramic or aluminium electrolytic capacitors(or even through-hole electrolytes) in ADC decoupling?
The ADC power input is basically pi-network(assuming we have cap near the supply) with exception that we have not 1, but 4 capacitors. Why not just use two capacitors(big and small to cover more frequencies shunting to ground). Putting two of identical capacitors pairs seems redundant, it would make sense to use different values like Dave says.
Not longer relevant, see comments.
- This question is more generic one, not only for this schematic. Often when it comes to inductors people just say "Oh, and here we have inductor". I am quite fascinated how people treat inductors like you can replace it with anything. How big the inductor should be? Does "bead" means that this is not actually an inductor, but a ferrite bead? Is it really so irrelevant and you can put in anything you have laying around, no matter if it is 10 uH, 10000 uH or small ferrite bead?