Re: gEDA-user: basic anti-EMI design q

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

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 <smeier@xxxxxxxxxxxxxxxxxxx> 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
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