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AMC7836: Pullup status of GPIOpins

Adrian Liu
Intellectual 920 points
Part Number: AMC7836

Hi Team,

My customer is testing with AMC7836, and they found the GPIO pin was not pullup when powered the 3.3V-IOVDD.

The GPIO was actually pullup after powered the 5V-AVDD/DVDD.

Could you help explain this test performance?

BR

Adrian

  • 0
    TI__Expert 4090 points

    Hi,

    A DAC engineer will get back to you after the US Holiday of July 4th.

    Thanks,
    Lucas

  • 0 in reply to Lucas Burnette
    TI__Expert 4090 points

    Hi Adrian,

    Based on the picture you shared, it appears that GPIO_OUT is being pulled up to the IOVDD voltage (3.3 V), correct?

    The device must be powered up completely for the GPIO functionality to match the device's datasheet.

    Footnote #2 mentions that DVDD/AVDD must be higher than IOVDD for normal device operation.

    Let me know if there are any other issues!

    Thanks,
    Lucas

  • 0 in reply to Lucas Burnette
    TI__Intellectual 920 points

    Hi Lucas,

    The test result is that if I only apply the IOVDD_3.3V, GPIO will not being pulled up. 

    And we can see that the GPIO will not being pulled up until the moment DVDD/AVDD applied.(The pic I shared)

    So my question is whether we should apply both IOVDD and DVDD/AVDD to pull up the GPIO_OUT?

    Because I did not find any connection between GPIO pin and AVDD/DVDD in D/S.

    BR

    Adrian

  • 0 in reply to Adrian Liu
    TI__Expert 4090 points

    Hi Adrian,

    I am checking with another engineer and will get back to you shortly.

    Thanks,
    Lucas

  • +1 in reply to Adrian Liu
    TI__Expert 5250 points

    Hi Adrian,

    If the device's DVDD is not powered on, the GPIO pins are pulled to ground via the device's internal circuitry. This is what you are seeing. Once the DVDD is applied, the GPIO pins go to Hi-Z, as specified in the datasheet for their startup level. 

    It is recommended to pull up both the IOVDD and AVDD/DVDD at the same time, or with minimal delay, to have the GPIO pins go into High-Z mode. 

    Let me know if you have any further questions.

    Thanks,
    Erin