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PCM2903C S/PDIF input reference circuits

Takumi Suzuki1
Mastermind 8430 points
Other Parts Discussed in Thread: PCM2903C, PCM2902C

Hi

Do you have a reference circuit of S/PDIF input?

There is just USB input reference circuit on the datasheet page26, to my regret.

Could you give me an S/PDIF interface circuit for PCM2903C?

Best Regards,

 

 

  • 0
    Expert 1720 points

    Hi,

    If you want optical S/PDIF (TOSLINK) that you can directly connect optical receiver like TORX147 from TOSHIBA or similar receiver from SHARP.

    If you want isolated electrical S/PDIF that you need to use pulse transformer for isolation and some BUS receiver for converting of voltage level from S/PDIF to 3.3V CMOS level output. For consumer S/PDIF you will need termination resistor 75R and for professional S/PDIF 110R resistor. Pulse transformer suitable for S/PDIF is DA102C, LL1572, S22083 or PE-65612. For bus receiver I used 75176B but it has +5V TTL output. You need to find something with +3.3V level output. You can inspire on my page with soundcard based on PCM2902C. http://www.pavouk.org/hw/usbcodecpcm2902/en_index.html

    When the chip detects correct S/PDIF signal that it automatically change input from ANALOG to S/PDIF.

    Best regards, Pavel.

  • 0 in reply to Pavel Ruzicka
    Mastermind 8430 points

    Pavel-san,

    Thank you very much for your detailed explanation.

    I understood well !!

    Best Regards,

  • 0 in reply to Takumi Suzuki1
    Mastermind 8430 points

    Pavel-san,

    Sorry let me understand well about "isolation S/PDIF".

    I think we usually use "Optical" or "Coaxial" interface.

    In case of optical, we use Optical devices and in case of Coaxial, we use termination(75ohm or 110ohm)+Capacitor.

    I do not know where we use "isolation" S/PDIF.

    Could you tell me more detail?

    Best Regards,

  • 0 in reply to Takumi Suzuki1
    Expert 1720 points

    Hi Takumi,

    If you use coaxial S/PDIF without isolation transformer that you can have troubles with ground loops between devices. It may cause bigger jitter of S/PDIF signal and hum or noise on analog part of your device. It is much better to avoid these possible troubles with using of pulse transformer on the S/PDIF inputs or outputs. Also combination with capacitor is good to prevent possible DC voltage on the input. For isolation are usually used these pulse transformers from more vendors: DA102C or LL1572 or S22083 or PE-65612. I tested them succesfully up to sample frequency 192kHz.

    Best regards, Pavel.