How to have separated ground pours for analog and digital

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kalbun
Posts: 12
Joined: 15 Jun 2010, 18:34
Location: Italy

How to have separated ground pours for analog and digital

#1 Post by kalbun » 15 Jun 2010, 19:03

Well... I write the first message in the forum, with a suggestion that was asked often in the old forum.

In several analog - as well as RF - circuits you need to separate various ground areas, to be connected in one point, possibly with a star configuration.
If you put two copper pours and join them with a trace, Diptrace assign both of them to the same netlist. This is not what we want.

Instead, put a zero Ohm resistor across the pours: this way, netlists remain separated, but from the electrical point of view you obtain the desired result.
"Scusate l'errore! E' che io questa convenzione dei segni non l'ho mai capita"
"Sorry for the mistake! Fact is, I still can't grab this current's sign convention"

(G.A. - assistant professor - lesson of theory of electronics)

Tedward
Posts: 30
Joined: 24 Jun 2013, 15:17

Re: How to have separated ground pours for analog and digita

#2 Post by Tedward » 24 Jun 2013, 15:34

I did this by creating a 'link' component that was just an 0603 with the 2 pads joined together by a track. This achieves the same as the author suggested but allows the analog and digital grounds to be 2 separate nets without needing an actual resistor.

Tryin1953
Posts: 1
Joined: 17 Aug 2016, 08:00

Re: How to have separated ground pours for analog and digita

#3 Post by Tryin1953 » 18 Aug 2016, 11:53

Tedward wrote:I did this by creating a 'link' component that was just an 0603 with the 2 pads joined together by a track. This achieves the same as the author suggested but allows the analog and digital grounds to be 2 separate nets without needing an actual resistor.

yeah! me too.. I also created link and same goes with yours, it allows the analog and digital grounds to be separated w/o actual resistor.

dslocum
Posts: 13
Joined: 05 Jun 2013, 19:03

Re: How to have separated ground pours for analog and digita

#4 Post by dslocum » 23 Sep 2017, 09:51

Could someone please post an example of this. I'm just not understanding this from the description.

Is this done in the Component editor?
How do I connect it in the schematic?

THanks

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KevinA
Posts: 444
Joined: 18 Dec 2015, 15:35

Re: How to have separated ground pours for analog and digita

#5 Post by KevinA » 23 Sep 2017, 14:44

A problem I have is the software delete nets with a single pin:
grounds.jpg
Which results in this:
grounds1.jpg
Notice the two pins without nets have a larger gap on the copper pour?
Why did DT decide to drop the ground connections? ERROR: Single pin in net: Net1, C3:1 / Net 2, C1:2

Update: Added a connector to get GND signals and tied the two grounds together with a simple trace in PCBeditor, no errors and the Gerber looks good.
ground2.jpg
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chchyong89
Posts: 4
Joined: 26 Dec 2016, 01:03

Re: How to have separated ground pours for analog and digital

#6 Post by chchyong89 » 10 Jan 2018, 23:43

I don't recommend separate analog and digital ground if there is no necessary, there should be always sharing a totally same ground potential for optimal performance.

Only separate it when either of them have large current source/sink on certain node, then you should use "keepout" to guide the current flow back to the zero potential node.

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