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TCA9509 DDC : HDMI compliance Test

na na78
Guru 16770 points
Other Parts Discussed in Thread: TCA9509

Hi

We use TCA9509 for DDC signal conditioning.  Actually, a trouble was solved by adopting TCA9509.

Then, we have the following question.

Is there any concern about meeting HDMI compliance requirement using TCA9509 in DDC line?

regards

  • 0
    TI__Genius 16510 points

    Hello Na na,

    Generally speaking: No, there are no issues with passing HDMI compliance testing since the capacitance of the pins is much smaller than I2C compliance spec.

    I have seen cases where the test procedure lined out in the CTS document can cause issues with the device, since it constantly will trigger the device's VIL and VIH levels. If the B side is facing out towards the HDMI port, I don't see any issues with the test. It is best to make sure the EN pin is pulled to GND for the test, to make sure the device itself does not interfere with the capacitance measurements, since the CTS says the test should be powered.

  • 0 in reply to Jonathan Valdez
    Guru 16770 points
    Hi Jonathan

    Thank you for your answer and I'm sorry for late reply.

    I don't get following.
    > It is best to make sure the EN pin is pulled to GND for the test,

    Pulling EN pin down to GND means Outputs are disable.
    Is it OK that we measure the capacitance of the device with outputs disabled?

    regards
  • 0 in reply to na na78
    TI__Genius 16510 points

    Na Na,

    The reason for EN pin to be pulled to ground is to prevent the device from pulling the bus to ground. If the device pulls the bus to ground during the test, then the test results will be incorrect. Capacitance measurements will not change if EN is pulled to ground.

    If you are applying the measurement to the B side, and make sure the A side is idle during the test, then the capacitance measurement will likely be unchanged if EN is high or low. You are trying to prevent signals from interfering with the capacitance test results.