Renesas detailed app note about grounds. Link here (PDF)
Ground is taken for granted. We stand on it, we dig into it, we make mud pies out of it. The ground isn’t supposed to move. We don’t have to think about it; it just is. When it comes to grounding a circuit, we assume that our connections are as solid as the turf below our scuffed shoes. Many times, this is a reasonable assumption-but not always. How do we know when there is a problem with a circuit’s ground? What practices will ensure we construct a good ground?
No longer to be taken for granted, we define ground in ideal and real situations. Ground configurations and printed circuit board (PCB) examples will be presented.