How to separate the Analog and Digital ground

Yu-Hung

Expert 1130 points

Hi,

I have a battery power for the sensor and system.

I use 0-ohm to separate digital and analog area.

But my sensor needs battery too, and the output is analog signal.

So, the system diagram shows in following figure.

My question is what the sensor's "Ground" is?

DVSS or AVSS?

For A/D converter, I thought the sensor ground should be connect to AVSS. (red dotted line)

Then Ground = DVSS = AVSS, all connect together..............I feel weird.........

In this case, how do I do?

over 10 years ago

0 Bob Benjamin over 10 years ago

TI__Guru** 113765 points

Hi Yu-Hung,

You might find the information at the following link helpful:

http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/grounding-techniques

Your sensor will need to be properly referenced to the ADC ground. It is the routing that is critical with respect to low level signals and return currents so that they are not passing through noisy digital paths. With grounding, sometimes a star grounding methodology is useful.

Best regards,

Bob B

0 Yu-Hung over 10 years ago in reply to Bob Benjamin

Expert 1130 points

Hi Bob,

Is this what you said?

Thered line is return path and not passing through digital circuit.

Best regards,

YHH

0 Bob Benjamin over 10 years ago in reply to Yu-Hung

TI__Guru** 113765 points

Hi YHH,

Yes, you don't want the return currents from the sensor to pass through the noisy digital section. This is also true for routing the power for the sensor.

Best regards,

Bob B

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How to separate the Analog and Digital ground