ADAU1701 ADC mapping

tommi Question

Sep 20, 2011 00:00

Hello everyone,

I think that the mapping of the two ADC's of ADAU1701 is the opposite of what's written in the datasheet.

Judging from Sigma Studio it seems like ADC0 is on PIN04 and ADC1 on PIN02 as it's witten in the Evaluation Board documentation (EVAL-ADAU1701MINIZ.pdf).

I am sure this is not a major issue, but being sure about this would help much in the design of stereo applications

Can anyone please confirm this or explain why the two documents, referring to the same device, read different?

Thanks

Audio Signal Processors

SigmaDSP Audio Processors

adau1701

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SteveL Reply

Sep 20, 2011 00:00

Hi,

I just went through the same experience as you. It would appear that there was an error in early versions of the ADAU1701 datasheet and ADC0 and ADC1 were shown with their pins swapped. The evaluation board was designed according to the datasheet and is therefore also incorrect.

The datasheet has now been corrected but it may be that the eval board info has not.

All this information comes from this earlier thread:

https://ez.analog.com/message/13235#13235

If you are already committed to hardware (as I am) then you simply need to adjust the routing in your SigmaStudio schematic.

Hope this helps!

Steve L.

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tommi Reply

Sep 20, 2011 00:00

Thank you for confirming this, Steve, but it still does not make that much sense to me...

I mean, on a practical basis I am quite sure that ADC 0 is on PIN 4 and ADC 1 in on PIN 2.

The ADAU1701 datasheet (latest version, just downloaded!) says the opposite, while the evaluation board documentation has it right.

Cheers

P.S.: Of course we have modified our Sigma Studio projects to bypass this issue!

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ADIApproved Reply

Sep 20, 2011 00:00

Hi Tom,

Actually, pin 2 is ADC0 (left channel) and pin 4 is ADC1 (right channel). This maps to the standard TRS (Tip-Ring-Sleeve) connector scheme of having the left channel on the tip and the right channel on the ring, with ground on the sleeve. You can test this by inputting a signal on the left channel only. You'll see the signal appear on the tip of the cable's connector, with no signal on the ring. This signal should then show up at ADC0 (pin 2), and in SigmaStudio, the signal should be present on channel 0 of the input cell.

An even more direct test would be to connect the signal directly the input resistor on the ADC, bypassing the plug entirely, and then check the readback value in SigmaStudio for both ADC channels.

I attached the most recent schematic of the EVAL-ADAU1701MINIBZ, which shows the proper connections.

It's possible that you have an older version of the board that might have been incorrectly designed, with the input channels swapped. I'll look into that.

Best Regards,
Brett

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tommi Reply

Sep 20, 2011 00:00

Hi Brett,

I did the test (even more brutally... directly on the PIN 02 of the chip! ) and you are absolutely right.

I will immediately update our development team about this.

Thank you very much for your help.

Regards

Tom

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