Ground for digital pots

Lukasz Przenioslo

Hello there,

I have a question regarding TI's digital pots (and digital pots in general I gues). They are digital components with a physical wiper of some sort i believe. In my applications where i had both digital and analog ground planes I have always connected the pots to digital ground as I thought of them as digital devices.

In some recent designs over the internet Ive seen that some people connect digital potentiometer ground to analog GND... Is that right? Wouldnt then the AGND plane take interference?

I would really aprichiate a clarification from someone that has more knowledge/ expirience than me with this topic.

over 11 years ago

0 Ramgopal Divakar over 11 years ago

Expert 1335 points

In many of our analog designs, we have a common ground plane unbroken for digital and analog. However we'd restrict the analog parts in analog area and digital in digital area and not cross the power planes over to the analog section. This seemed to improve our performance.

Walker

0 Lukasz Przenioslo over 11 years ago in reply to Ramgopal Divakar

Expert 2630 points

So... Digital ground for digital pots then or analog coz I you didnt quite answer the question :P.

0 Ramgopal Divakar over 11 years ago in reply to Ramgopal Divakar

Expert 1335 points

AGND = DGND = One common ground plane so there is no isolation in terms of grounds.

0 Lukasz Przenioslo over 11 years ago in reply to Ramgopal Divakar

Expert 2630 points

No isolation yes, but the ground are connected in STAR for example, or at least in only 1 point. The question remains.

0 Ramgopal Divakar over 11 years ago in reply to Lukasz Przenioslo

Expert 1335 points

Then I do not know. I was referring to a case where there is one common plane for all and you can call that net "GND" so no question of star arises. If you have two net names then they can be tied at once place. So I do not know how to answer your q

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Ground for digital pots