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ADC128S022: what happens if VA ramps slower than VD?

Adam Daluga
Expert 5790 points
Part Number: ADC128S022

Hello,

Can you let me know what happens if VA ramps slower than VD?  What happens if the ESD diodes are turned on?

Will the data be corrupted until both voltages are up or does the part get damaged in some manner.

Thanks,
Adam

  • 0
    TI__Expert 5260 points

    Hi Adam,

    Thanks for your question. The recommendation is for your VD to not exceed your VA by more than 300mV as this will turn on the ESD diodes and also violate the absolute maximum rating of VD (max = VA+0.3V, up to max of 6.5V), which may cause permanent damage to the device. The shared ESD resources are similar to the input pins, shown in figure 37 of the datasheet:

    When the ESD diodes are turned on, the current will be redirected to VA. The redirected current may violate the absolute maximum rating, found in section 6.1 of the datasheet, for current to any pin (max = ±10mA), which will cause damage to the device.

    I hope this helps.

    Best,

    Samiha

  • 0 in reply to Samiha Sharif
    TI__Expert 5790 points

    Thanks Samiha,

    The catch is I am worried about timing not amplitude.

    If you meant to say do not let VA power up by more than 300ms after VD, then we are good since the delay I simulated is about 23us.

     

    If this 23us is going to be an issue, I will have to slow down the power up of VD which means some deadbug parts since the board is already made.

    Please let me know, thanks!

    Adam

  • 0 in reply to Adam Daluga
    TI__Expert 5260 points

    Hi Adam,

    The datasheet doesn't specify a particular minimum delay, so you should be fine as long as VD does not exceed VA by more than 300mV at any point. Since your duration is so short (23us), it may not be an issue but this may still damage the device over time.

    Best,

    Samiha