A/D Ground plane separation and common supplies

[rtarbell]

I am using a PGA2320 digital volume control pot for an amp; for its analog power supplies, I am using +/- 8V regulators fed via a wall wart.

Concerning the separation of digital and analog grround planes, I am trying to use just one main power supply (a 12V wall wart). I can get +8V analog from the 12V by a voltage regulator, and I can get -8V from the +12V wall wart by a charge pump (Microchip TC962 can take the +12V and turn it into -12V) and voltage regulator.

I can also get +5V for the digital controllers via a 5V voltage regulator. If I do this, will this violate the separation of analog and digital ground planes because the analog supply regulators and the digital supply regulator are being fed from the same wall wart?

[jcx]

usually analog and digital gorund are connected, there are just some considerations for where/how relative to signal inputs/outputs for digital and analog portions of the circuit

a solid ground plane with analog and digtial parts seperated as well as is logical would be a start, then performance may sometimes be improved slightly by putting some slots that partially seperate analog and digital ground planes except for one narrow neck of common copper

read all of the grounding tech notes you can find, some GHz speed layout techniques don't really translate to most audio apps but the principles are worth understanding

the 1st is that current always flows in closed loops - then consider that "ground" has impedance both AC and DC that converts ground return portions of the current loops into ground noise/common impedance coupling

the goal is to keep high current and high frequency "dirty ground" return currents from having/wanting to flow in the analog ground