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TMDS261B/361B - Temperature variation of equalizer gain

Guru 19775 points
Other Parts Discussed in Thread: TMDS261B, TMDS361B

Hi Team,

Could you please tell me about the gain of TMDS261B and TMDS361B ?

Our customer is evaluating their system using 10 to 20m HDMI cable. When the ambient temperature rose to 40 degrees Celsius, there were 1 device out of 12 which could not pass the video signal. I understand the equalizer gain is adaptive, however, does the gain curve varies when the temperature change ?

How much would the gain vary when the temperature changes over the recommended temperature range ?

Do you have Gain vs Temperature characteristic ?

Best Regards,
Kawai

  • Hello Kawai,

    I will look for this information.

    What is the cable length on the failing case, 10m or 20m?

    Can you get eye diagrams of the failing case?

    Regards.

  • Hi Elias-san,

    Thank you for your support.
    I have asked our customer about above information.

    The issue occurs at 20m HDMI Cable. It could pass the video signal at 20m, however it sometimes has noise on the video that it seems it does not have enough EQ gain at room temperature.

    When the temperature rises, it will not be able to pass video signal. So, it is thought that EA gain is decreasing as the temperature rises.

    I have asked for waveform data of the TMDS261B input, but they told me that it is difficult for them to get a waveform data in their system.

    Best Regards,
    Kawai

  • Hi Elias-san,

    I apologize that I could not get the waveforms, but I would appreciate it if you could give me your update about the temperature variation of equalizer gain.

    Best REgards,
    Kawai

  • Hello Elias-san and team,

    Can you kindly update the information for Kawai-san?

    Thank you very much for your support.

    Best regards,

    Daisuke KAWASAKI

  • Hello,

    I've just sent you an email with some information.

    Regards.

  • Hi Elias-san,

    Thank you for the information.

    Please let me ask you one more thing.

    Do you know how the EQ gain is affected only with temperature variation ?
    When the temperature increases would the gain typically decrease or does it increase ?

    I would appreciate it if you could give me your opinion as a general equalizer characteristic.

    Best Regards,
    Kawai

  • Hello,

    Please see below answer from Design:

    The EQ gain should have little dependency on temperature since the EQ gain is defined as the gain difference at low and high frequencies. When the temperature changes, both high frequency and low frequency gains change in a similar way. That results in a relatively stable EQ gain.