Analog audio to S/PDIF

The PCM2902C from texas is an Stereo Audio DAC With USB Interface, with S/PDIF Output and stereo analog input.
To me its only the analog input and S/PDIF output which are of interest and question is if it is possible to utilize these
features without having to use the USB interface.

This means that what I really really want is a single chip solution which encodes a stereo single ended analog input
(or even a balanced analog input) to S/PDIF. I have not found any such solution which also comes in a small package less
than tqfp32, ssop20/28 etc or similar. Only larger multifeature packages which would be far above overkill in my design.

There are many solutions that I have found but noting small and neat, thats why I hoped that the solution from Texas could be
used without using the USB interface.

A brief look to the block diagram suggests that the device isn't suitable.



The S/PDIF output is connected in parallel to the DAC, you would need a loopback over USB to send the ADC data to the output.

Maybe, but I am not so sure if it really is so or that the block diagram actually tells the whole truth.
Heres a snippet from the datasheet. page21:

The PCM2902C employs both S/PDIF input and output. Isochronous-out data from the host are encoded to the S/PDIF
output and the DAC analog output. Input data are selected as either S/PDIF or ADC analog input.
When the device detects an S/PDIF input and successfully locks the received data, the isochronous-in transfer
data source is automatically selected from S/PDIF itself; otherwise, the data source is selected to ADC analog
input.

This feature is a customer option. It is the responsibility of the user to implement this feature

Click to expand...

This makes me wonder. If there is no host the chip may select its own source if detected and spit out as S/PDIF, hopefully.
The last sentence defining it as a customer option is also difficult to understand. Finally, what are the SEL0/1 inputs which
has to be set high... Factory testing options, may these enable an internal loopback?

Nevertheless, a dedicated chip without a questionable USB functionality would be prefferable..,.

The auto-detect feature is clearly referring to selection between ADC and S/PDIF input. SEL0/1 are specified as required H level, apparently test related.

Maybe, but I am not so sure if it really is so or that the block diagram actually tells the whole truth.

Click to expand...

There are no indications of a loop-back feature in the datasheet.

You are prob. right. I clearly do not understand the concept or I just wished upon a star. To bad. Never the less, thanks for the clarifications

So.... You have not seen any single chip analog to s/pdif encoders that might fit my needs on your way?

Breg

NXP UDA1355H should do, QFP44 however.

FvM said:

NXP UDA1355H should do, QFP44 however.

Click to expand...

Yes, I have been looking at that one earlier, in addition to Analogs ADAV801/2/3 series. The UDA1355H however is obsolete so therefore I dropped it, but I guess for my 3-4 series I may get a few samples on ebay ore somewhere. But the few samples I found there is quite expensive. It does the job however .. And 12by12mm QFP aint that big anyway. NXP did not point out any replacement though.

The ADAV80x series is LQFP64 but still cheaper than old UDA1355H, but again in a bigger package.

I have to consider ops and cons