a question about ADC grounding

Dear All: I have a question about ADC grounding. In the "Sensor Signal Conditioning" published by ADI, the grounding is recommanded to connect only in the power supply. Also the ADC is regarded as analog device and is grounded to AGND. My question is that if AGND and DGND is connected only in the power supply, the current from DAC to buffer will flow through DGND - power supply -AGND too. It's a big current loop, isn't it? Will it bring noise to ADC's AGND? Or I should use another ground method?

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The basic principle of what you want is a "star ground". The ADC, DAC and other digital grounds all connect back to the one point (hence a "star" shape to the grounds). There should be no ground loops.


Reply to
David L. Jones

One can't really answer without knowing a lot of specifics, but 98% of the time a pc board should have a single, solid ground plane. The ADC analog and digital ground pins, if it has distinct ones, should be nailed directly to that plane. The ground plane should be bolted directly to the case as many places as possible.

If you're dealing with low-level signals, handle any ground-loop or similar issues locally.

Many vendor app notes and recommendations are silly. They may be workable on a demo board, but real life is more complex.


Reply to
John Larkin

"John Larkin" a écrit dans le message de news: snipped-for-privacy@4ax.com...

I fully agree with John. A full solid ground plane will make 98% of the designs working nicely, and a splitted ground plane will make things worst

98% of the time (especially for EMC immunity tests) except in very specific cases that would need to be handled with great care and knowledge. Just a complement : In order to avoid nasty currents in the ground plane the best way is to think twice at the component placement stage, and to avoid placing the ADC between two noisy digital sections. For example if the ADC is on a corner of the PCB with the analog parts and inputs just close to him then there is far less risks of ground noise...

Cheers, Robert

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Reply to
Robert Lacoste

Thank you all! Sorry, can I upload a image to make the explaination more clearly?

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