ADAU1761 grounding
Thread Summary
The user asks if the exposed pad of the ADAU1761 is internally connected to both AGND and DGND, and if tying it to the AGND plane in a split ground design could create a ground loop. The final answer confirms the exposed pad is connected to the substrate ground and recommends tying it to the AGND plane if a split ground is necessary, but strongly advises using a single ground plane to avoid potential issues. The ADAU1701 evaluation boards also use a single ground plane, and no performance advantages have been observed with split planes.AI Generated Content
From the data sheet I read:
NOTES
1. THE EXPOSED PAD IS CONNECTED INTERNALLY TO THE
ADAU1761 GROUNDS. FOR INCREASED RELIABILITY OF THE
SOLDER JOINTS AND MAXIMUM THERMAL CAPABILITY, IT IS
RECOMMENDED THAT THE PAD BE SOLDERED TO THE
GROUND PLANE.
I am planning to have a split ground plane. I would typically tie the the DGND
and AGND together at one point (through a low ohm resistor). Is the data sheet
saying that the two AGNDs and the DGND are tied internally to the exposed pad?
It was my intent to have the copper rectangles under the device tied to AGND plane
and then have the DGND connection go to the single connection point. Would this
create a ground loop?
Thanks
Audio Signal Processors
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SigmaDSP Audio Processors
adau1761
grounding
Processors and Microcontrollers
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The paddle (exposed pad) is electrically connected to the substrate of the die, which is at ground. If you must have a split ground plane, then we would recommend that you tie the exposed pad to your analog ground. However, I should emphasize that we do recommend a single ground plane on your board. We haven't seen performance advantages in our converters by using split planes, and rather, trying to use separate analog and digital ground planes seems to cause more problems than it attempts to solve.
The ADAU1701 evaluation boards do not have split ground planes, either. Unless you're very, very careful with your layout and know your return current paths, split ground planes can often cause more problems than they attempt to solve. In general, we'd recommend that you use a single ground plane.
Is this the case with the ADAU1701 as well? I have been keeping DGND and AGND seperate in my design, but you haven't found any performance difference, then I won't bother anymore.
I have made some suggestions regarding PCB layout here:
https://ez.analog.com/docs/DOC-1889
We generally follow these practices when designing SigmaDSP and audio codec evaluation boards.
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