Hi Kai, Thank you very much for your reply.

This layout would be good, if all the different supply voltages were totally separated. But mostly they aren't. If they come from the same power supply unit, then some capacitive coupling will exist, resulting in a certain ground loop for high frequent digital currents.

If I use two separate supplies right from the transformer i.e. If I use a transformer with two secondaries with one after rectification, filtering and regulation feeding Analog section and the other secondary feeding the digital section. How much would doing this help and I see no GND loop as well since transformer windings are galvanically isolated.



Again, I would suggest you to use the scheme I posted in my last reply. Connect all the individual grounds at this certain single ground point. Do also connect the chassis ground to it.

You mean, If I am connecting the two gnd planes Agnd and Dgnd under the ADC then at the same meeting point I should connect all other Gnd in my circuit [ apart from Agnd and Dgnd ]. The chasis Gnd i.e. The Third Phystical Earth wire should be conncted at the meeting point.

And if you must cross the separated ground planes, then don't forget to introduce a series impedance, where the signal traverses the gap. Otherwise you connect the both ground planes together again at this point via stray capacitance and introduce a ground loop for digital ground return currents...

I am a bit confused with above statement. Do you mean laying inter plane tracks should be avoided at all and if it is really required to run a track from one plane to other plane then at the plane crossing place a resistor of some value say 10 Ohms must be put in the track. Did you mean a small resistor when you said impedence or some other thing? Were you refering my zero cross track shown in earlier picture?

Thanks & Regards,
Prahlad Purohit