- thanks! I like this "Ferrite beads can be effectively used as a part of "PDN filter" in very specific cases. It is a scalpel - not a blunt sword"
I am beginning to realise I may be overthinking many aspects here - looking at many designs you see many different approaches to the same problem and many solutions. In some cases they are simple designs, low component counts etc. There may be excessive noise or other issues, but for the most part it probably don't cause enough of a problem that the extra design effort and component count makes it worthwhile to eliminate. On the other end of the spectrum you have systems designed for industrial use where the reduction of noise is taken to the extreme - where as much noise between circuit blocks is filtered, but also great care is taken such that noise from the outside is not coupled in, and that the device will not radiate noise. The simpler designs are probably more concerned with eliminating radiating interference (for compliance) whereas the latter designs are looking to be stable and reliable in as many installation areas as possible and so take a more cautious/over-engineer route.
it would also appear that designers start with a simple design; simulate, test, measure and then rectify the issues they find. Over time they build up a knowledge-bank based on experience and are then able to predict issues that may
happen as they've seen them before and so include remedies in future designs.
Over the last few days I have spent a lot of time talking to many people on many aspects of design - from these conversations there seems to be a case to be made that "noise" is an extremely complex (and often unpredictable) part of the real world. With enough experience you can predict issues, but as robertferanec
showed in his videos, you can still be caught out - you can't always predict everything.
Instead you design the project to the best of your knowledge and experience and test it. You may run some simulations etc. It is then more important to be able to find the source of noise or interference in your case
- there is not a one-size-fits-all-solution.. the designs that are out there are not guaranteed, the solutions work in their situation, but you need to sort out your own design for your own issues (maybe our boards are different materials, more or less layers, longer or shorter tracks etc - there are just too many variables at work). But even then you might get caught out... that's what HW revisions are for.
Now having said all this, there is a wealth of knowledge and experience out there that we can take advantage of - and there are common problems with common solutions, and so of course take advantage of that. At the end of the day, design for what you need - if you can cut a component without sacrificing performance/functionality/reliability/stability (or that sacrifice is deemed acceptable) then go for it.