analog ground & digital ground

[{ antonio }]

is there a differnece between the 2 and can can i connect the 2 to the same ground.  

thanks in advance.

[zeta55]

As I understand it it's the same ground but you keep them seperated as analog to one point and Digital to one point. Make sence??

[The Tone God]

Yes and no. They are the same ground in the end but there is a reason to seperate the two grounds.

With digital stuff with all the logic state's shifting noise gets into the system. As long as the noise does not go above logic thresholds everything is ok. The digital will work normally ignoring the noise. This is one of the nice things about digital.

The trouble comes with the analog portion of the circuit. Unlike digital where the shifting is ignored in analog land ANY voltage change is recognized and thus becomes noise.

For these reasons, and others, the noisy digital ground and noise sensative analog ground are kept seperate and then tied at one point in the circuit.

This is not a complete answer but a quick overview.

Andrew