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TUSB1064: When AUXn 1.3V

Kevin Huang8
Genius 4891 points
Part Number: TUSB1064


Hi 

If AUXn voltage level under 2.7V, Hwo to varify TUSB1064 AUXn or suggest other part number?

 

 

  • 0
    TI__Mastermind 47121 points

    Hi,

    I'm not sure I fully understand the question. This looks to be an issue with the common mode voltage.

    What issue are you seeing in functionality?

    Are the AUX PUP and PDOWN resistors implemented correctly?

  • 0 in reply to Vishesh Pithadiya
    Genius 4891 points

    Hi 

    Because the TUSB1064 has a voltage limitation for AUXN devices, requiring a voltage higher than 2.7V, are there any components with a wider voltage range?

    For example, the DELL XPS NB's output voltage level is only 1.3V, which causes it to not display an image.

  • 0 in reply to Kevin Huang8
    TI__Mastermind 47121 points

    Hi Kevin,

    This voltage of 2.7V is derived form the DisplayPort specification. 

    This is what the AUX channel should look like as per the DP specification.

    For AUXp, we see that there is a PDOWN(100k) present at the source, and a PUP(1M) present at the sink.

    For AUXn, we see that there is a PUP(100k) present at the source, and a PDOWN(1M) present at the sink.

    The PUP goes to 3.3V in both cases.

    This creates a voltage divider network setting the common mode voltage of the AUX. If the AUX common mode voltage is not set correctly DisplayPort signaling may not work.

    The 2.7V requirement is not an arbitrary part requirement but rather a requirement of the DisplayPort spec itself. If your system cannot meet this requirement, there is something in the system pushing it out of DisplayPort spec.