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Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Ground Pours on a DAC PCB.
Ground Pours on a DAC PCB.
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Old 24th December 2018, 06:32 PM   #11
MarcelvdG is offline MarcelvdG  Netherlands
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To me it's an open question whether or not it's a good idea to split ground planes at all; two former colleagues of mine were very much in favour of having one and only one ground plane because they never managed to get split-ground-plane PCBs to work properly.

If you do split them, connecting them at the DAC seems to be the most logical solution. It results in the smallest detour for the return currents of signals that cross the boundary between digital and analogue.
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Old 24th December 2018, 06:39 PM   #12
Markw4 is offline Markw4  United States
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Agreed, one ground plane can be fine. However, its still probably a good idea to think about where ground currents are flowing. For example, if most of the digital circuitry is in one area of the circuit board, the ground return connection to its power supply probably should be located around there somewhere and not necessarily next to the analog ground return connection at the other end of the circuit board.
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Old 24th December 2018, 06:45 PM   #13
MaverickPT is offline MaverickPT  Portugal
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Thank you all for your replies! It has been really informative!

This leads me to my next question. Is a regular "trace connection" good enough, or should I connect the different ground traces with ferrite beads!?
Would it provide any tangible benefit!?

Thank you and merry Christmas!
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Old 24th December 2018, 06:52 PM   #14
rayma is offline rayma  United States
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Quote:
Originally Posted by MaverickPT View Post
Is a regular "trace connection" good enough, or should I connect the different
ground traces with ferrite beads!?
Ground traces should always be as low impedance as possible.
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Old 24th December 2018, 06:54 PM   #15
MaverickPT is offline MaverickPT  Portugal
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Quote:
Originally Posted by rayma View Post
Ground traces should always be as low impedance as possible.
No ferrite beads! Got it!
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Old 24th December 2018, 07:23 PM   #16
MarcelvdG is offline MarcelvdG  Netherlands
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No beads and as short a connection as possible to the ground plane.
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Old 24th December 2018, 07:44 PM   #17
MaverickPT is offline MaverickPT  Portugal
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Quote:
Originally Posted by MarcelvdG View Post
No beads and as short a connection as possible to the ground plane.
Thank you!
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Old 25th December 2018, 04:01 AM   #18
deusex3 is online now deusex3  Russian Federation
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Quote:
Originally Posted by rayma View Post
Ground traces should always be as low impedance as possible.
This is the must for the RF circuits only
[Markw4=rayma;]Agreed, one ground plane can be fine.[/Markw4]
There are may be occur additional interferences from DGND to AGND in this case
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Old 25th December 2018, 05:53 AM   #19
Thorp is offline Thorp
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Quote:
Originally Posted by deusex3 View Post
This is the must for the RF circuits only


There are may be occur additional interferences from DGND to AGND in this case
Why it (the low GND impedance) is a must for the RF circuits only? We are talking here about 22.xxxx - 49.xxxx MHz frequencies or even higher for ESS chips.


That is why the star ground under the DAC chip is the best solution. The different currents will flow on the shortest way and the interferences between the different currents will be extremely low.


The star ground "ideea"should also be respected even there is a dedicated ground plane on a 4 layers PCB project.
I have got very good results with 2 layers PCB also, but I had to use 2 ground planes carefully inter-connected, one on each PCB side and a mirror placement of the DAC chips (it is a dual mono DAC project).
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Old 25th December 2018, 06:46 AM   #20
deusex3 is online now deusex3  Russian Federation
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Quote:
Why it (the low GND impedance) is a must for the RF circuits only?
I have mean what it is more relevant for RF , for 50 MHz this is much less important
Quote:
That is why the star ground under the DAC chip is the best solution.
Is it new design technique la "star ground" by Thorp ?
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