Dear All

What is the difference between the analog ground and digital ground. what is the real application of that. Especially this kind of separation we can observe for ADC application. What is the advantage over by separating digital and analog ground. even though finally it will connect together.

 

digital device work from the assumption that a voltage below 0.8 volt (TTL) is considered a digital low while a higher voltage i considered a digital high.

So the Vdd must be clean so as Vss (ground) because noisy ground can induce false logic states creating a real mess in understanding the results.

It is alway a good practice to keep the two grounds separated using optocoupler when necessary.

Alberto

 

Asume that digital gnd is swapping back and forth 1 ampof toggling current.If you tie and analog amplifier to this gnd it will see the I*R drop as signal. So when you layout the pc board you run analog gnd separate so it doesn't see these I*R drops as signal. EVENTUALY it will be tie together yes but as I call it at a holy point. daisy chain the ground can cause sometimes the whole circuit not to work.