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DS90UB928Q-Q1: How to set LVDS output to 0V (with I2C active)

user5163865
Genius 4120 points

Part Number: DS90UB928Q-Q1

Tool/software:

Hi,

I would like to turn off the LCD while the DES I2C line is active, but there would be problems if voltage was left applied to the LVDS line(TxCLKOUT＋/- 、TxOUT＋/-), so is there a way to fix the bus to completely 0V?
Because it is differential, I don't think the individual single-ended outputs will go to 0V even when low.
Also, referring to Table 5, it looks like it cannot be set to Hi-Z when it is active.

Best regards,
Hiroshi

  • 0
    TI__Mastermind 24835 points

    Hi Hiroshi,

    The 0x4A[0] = 1 register assignment will disable the output OLDI drivers of the DS90UB928, but there will always be a small current applied at the output voltage lines while the device is active. Paired with 100-ohm termination, this may always produce some non-zero voltage at the output.

    Please let me know if there are any other questions.

    Best,

    Miguel

  • 0 in reply to Miguel Bolante
    Genius 4120 points

    Hi Miguel-san,

    Thank you for your quick response.

    There seems to be no explanation for 0x4A in the D/S register map. Is this a hidden register?

    Best regards,
    Hiroshi

  • 0 in reply to user5163865
    TI__Mastermind 24835 points

    Hi Hiroshi,

    This register is not shared publicly as it overrides the power configuration of the LVDS driver. Usually, this is set to power on by default to avoid bring up sequencing issues, and the register is normally used for debug purposes (in this case, you may need to utilize it to initialize the device before driving the LVDS).

    Please let me know if you have any further questions.

    Best,

    Miguel