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  • TI Thinks Resolved

HDMI/DVI Digital isolator

Hi Colleagues,

Do we have any product or app note on how to galvanically isolate HDMI/DVI signals?

Kind Regards,

Carlos S.

TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • Hi Carlos,

    We unfortunately do not have an isolator designed specifically to isolate HDMI/DVI signals. Our fastest digital isolator is capable of 100Mbps data rate. Would that be good enough for your application?

    Regards,
    Anand Reghunathan
  • In theory, it should be possible to terminate TMDS signals into a bunch of LVDS isolators. However, the TMDS clock frequency can be anywhere between 25 MHz and 680 MHz, depending on the resolution.
  • In reply to Clemens Ladisch:

    Thank you Clemens.

    This is a standard 1080p 60Hz Full HD stream, to clarify.

    Would you be able to elaborate some more on a possible solution and part number?

    Kind Regards,

    Carlos S.

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    The ISO7820LL would be a two-channel LVDS isolator. (HDMI/DVI use four channels.)

    TMDS uses current mode logic. I've found an application report (SCAA062) that shows how to interface CML and LVDS.

  • In reply to Clemens Ladisch:

    Hi Clemens,

    Thank you for your input on this matter.

    I'm not really educated on this subject, so my understanding from the above is that HDMI uses TDMS, therefore a type of CML, which can then be converted to LVDS. Is my assumption correct?

    Also, can you describe how to calculate the required bandwidth for an HDMI/DVI signal? I would assume this would only depend on the refresh rate and resolution, but perhaps I'm being overly simplistic.

    Kind Regards,

    Carlos S.

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    Yes, CMS is the physical layer for TDMS.

    According to Wikipedia (section "Refresh Frequency Limits at Various Resolutions"), 1080p at 60 Hz requires 3.2 Gbit/s, which corresponds to 800 Mbit/s on the four TDMS channels.

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