Digital ground and analog ground have to get tied together some where. Think of the ground path being the return of an electrical circuit. All seperating the grounds out does is to have the single ended analog signals return signals not getting mixed in with the digital return signals. Yes noise on one side will propigate through to the other but.... an inductor along with the capacitance between the planes will significantly lower the short term amplitude.
So the operative word is immediately... remember the idea of an inductor is that the current flowing through it can not change instantly. Steve Meier Phil Taylor wrote: >Steve Meier <[EMAIL PROTECTED]> wrote: > > >>I also use seperate >>ground plains (the return path) and tie the analog ground to the digital >>ground with a power inductor. >> > >Steve, how does this work? It'd seem like any spikes getting into the analog >side (or even an analog signal transient) would return thru this inductor >(that ties gnda to gndd) and immediately cause the entire analog ground to go >high? This seems contradictory. > >pt > > > >
