+ Post New Thread
Results 1 to 7 of 7
  1. #1
    Full Member level 1
    Points: 3,039, Level: 12
    zainka's Avatar
    Join Date
    Nov 2004
    Location
    No(r)way
    Posts
    115
    Helped
    4 / 4
    Points
    3,039
    Level
    12

    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.

    •   Alt14th January 2018, 14:19

      advertising

        
       

  2. #2
    Super Moderator
    Points: 243,734, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    42,341
    Helped
    12889 / 12889
    Points
    243,734
    Level
    100

    Re: Analog audio to S/PDIF

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

    Click image for larger version. 

Name:	pcm2902.png 
Views:	4 
Size:	74.5 KB 
ID:	143965

    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.


    1 members found this post helpful.

  3. #3
    Full Member level 1
    Points: 3,039, Level: 12
    zainka's Avatar
    Join Date
    Nov 2004
    Location
    No(r)way
    Posts
    115
    Helped
    4 / 4
    Points
    3,039
    Level
    12

    Re: Analog audio to S/PDIF

    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
    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..,.



    •   Alt14th January 2018, 17:02

      advertising

        
       

  4. #4
    Super Moderator
    Points: 243,734, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    42,341
    Helped
    12889 / 12889
    Points
    243,734
    Level
    100

    Re: Analog audio to S/PDIF

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



  5. #5
    Full Member level 1
    Points: 3,039, Level: 12
    zainka's Avatar
    Join Date
    Nov 2004
    Location
    No(r)way
    Posts
    115
    Helped
    4 / 4
    Points
    3,039
    Level
    12

    Re: Analog audio to S/PDIF

    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



    •   Alt14th January 2018, 18:35

      advertising

        
       

  6. #6
    Super Moderator
    Points: 243,734, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    42,341
    Helped
    12889 / 12889
    Points
    243,734
    Level
    100

    Re: Analog audio to S/PDIF

    NXP UDA1355H should do, QFP44 however.



  7. #7
    Full Member level 1
    Points: 3,039, Level: 12
    zainka's Avatar
    Join Date
    Nov 2004
    Location
    No(r)way
    Posts
    115
    Helped
    4 / 4
    Points
    3,039
    Level
    12

    Re: Analog audio to S/PDIF

    Quote Originally Posted by FvM View Post
    NXP UDA1355H should do, QFP44 however.
    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



--[[ ]]--