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Please help to provide a I2C redriver/buffer for HDMI cables.

liu zhiyuan
Prodigy 66 points
Other Parts Discussed in Thread: P82B715, TCA9803

Hi TI engineers,

We are working on an HDMI board to drive an HDMI screen with a long cable(about 10m).

Now with some newer displays the board working fine, but with some old displays (produced years ago) it may not work.

Finally, we found that old display with a long cable has a large capacitance in the i2c bus.

So, could you help to suggest an I2C redriver/buffer to us to extend the I2C drive strength?

I noticed P82B715, but this chip is required to be implemented on both sides of the long cable, however, we can only add to our design, but not the display side.

By the way, can P82B715 be added only on our board side?

Thanks!

  • 0
    TI__Guru 53555 points

    Hi Liu,

    Yes, P29B715 can be added to only one side as long as the appropriate pull-up voltage is used on both sides. This device is designed to increase the strength of the local signal driver in order to drive I2C communication over large capacitive loads like cables. This device would only increase the strength of the signal source and not the display, so this will likely not be the best solution here. 

    A buffer device such as TCA9803 may be more suitable here where only one side of the I2C bus is under your control. This device will buffer the line capacitance on either side, decreasing the overall capacitive load on the cable-side. However, this may still not be sufficient as the monitor will still be responsible for driving the capacitance on the cable. This buffer would only remove the capacitance that would be added by your design up until it connects to the cable. 

    Apart from these two solutions, there's not much more I can recommend to improve the capabilities of monitor-side communication through the cable. Do you have access to the cable itself? Or only the components on the far-side of the long cable?

    Regards,
    Eric Schott