How to connect the digital GND and Analog GND

[srinivasa]

Hi

Please anyone guide me how to connect the digital GND and analog GND.Any procedure is there for connection like between them a ferrite bead .

Thanks in advance
Srinivasa

 

[dknguyen]

Simplest way is just to treat them as the same ground and have them share a single ground plane. If you are using a breadboard this is really your only option- other options just cause trouble.

Or you could have two separate ground planes connected by a bridge at only one point (called a split-plane). But with a split-plane you have to be careful about some things or results will be worse than if you just used a single ground plane . The most important is to never route traces on other layers so they cross the gap between split planes. They must always only over the bridge where the split planes connect. THere are also different ways to bridge the split planes together. YOu can use a ceramic capacitor, or two anti-parallel schotkey diodes, or simply connect them directly via copper. I'd just connect them via copper but each method has advantages and disadvantages. The most important thing is to only route traces that cross split planes over the bridge and never across the gap. See attached PDF.

 

[crutschow]

The most important thing is to only route traces that cross split planes over the bridge and never across the gap. See attached PDF.

That's true for high speed analog and digital signals, but is not that critical for low frequency AC or DC signals. For high frequency signals you are concerned about keeping the return currents in the ground plane close to the signal line which means the signal line shouldn't cross the gap. For low frequency or DC circuits this is not a significant factor.