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Old 1st July 2004, 11:37 PM   #1
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Default WM8816 question

Hello

I'm a little bit confused, in WM8816 datasheet it says that AVDD & DVDD pins must be tied together in all designs because damage can be caused if supply voltages differ to any degree.

But in WM8816 Ev. board datasheet they have one 7805 for each AVDD & DVDD.

Whats the way to go? Split groundplane and split AVDD & DVDD or split groundplane and use the same supply for AVDD & DVDD.

This is my first pcb layout ever so plz let me hear your opinion.
Just wanna know if its totaly wrong and so on.

The traces for the controller is'nt there yet...

Layout & Top and Bottom Eagle 3D files (warning BIG .bmp files)

/Thanks in advance
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Old 1st July 2004, 11:39 PM   #2
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Oh, and this is 1 channel balanced. Eagle freeware you know...
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Old 2nd July 2004, 09:24 PM   #3
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Someone? grondplane question.
.bmp gone .jpg now on my homepage
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Old 2nd July 2004, 09:25 PM   #4
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Oh, supplyquestion I mean.
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Old 2nd July 2004, 09:40 PM   #5
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Tobias,

I have the eval module for testing, you are right there are separate regs. I think they mean that the supply levels should be the same, NOT that they should be physically tied together, that would make no sense.

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Old 14th July 2004, 09:49 AM   #6
Robin is offline Robin  United Kingdom
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I have had communication with Wolfson recently on this point and they tell me that the recommendations in the datasheet are recommended over what is suggested in the eval design. . Apparently, their advice these days is that the supplies (AVDD and DVDD) DEFINITLY need to be tied together from the same supply. Their communication was as follows:

"We would strongly advise that the AVDD and DVDD power supplies are connected to the same supply. There is a slight inconsistency between the schematic in the Evaluation Manual and the datasheet as the schematic is based upon the evaluation board, which has separate regulators with power supplies taken from the same input terminal, while the datasheet is more recent and amended much more regularly.

All applications advice should be taken from the datasheet while the schematic should only be used for layout ideas only, it is not really meant as an absolute reference design. There is no plan to change the Evaluation Board design. Running from the same supplies will not have an affect on performance. I hope this will not cause you any inconvenience.
"

I hope this helps some of you guys out there experimenting with this device.

Robin
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Old 14th July 2004, 01:32 PM   #7
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Thanks Robin! that helped alot.

So, is it really any idea to split groundplane if lets say I'm only gonna have input -> WM8816 -> OP -> output ?

/Tobias
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