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ADS1115: Max Rating

McKenna Strambi
Intellectual 1530 points
Part Number: ADS1115

Tool/software:

Hi expert,

In our design we are powering ADS1115 with 3.3V. In a normal use case, AIN0 and AIN1 pins will have voltage less than 3.3V. However, occasionally they will have 3.8V present on them, which is 0.2V higher than the absolute maximum rating. 

Below are the questions we have. 

  1. We are wondering if there is a margin built into this VDD+0.3V maximum rating on the AINx pins. 
  2. Would the AINx pins be able to tolerate 3.8V for a short amount of time (vs a long period of time)? If yes, how long would that be?

Thank you!

McKenna

  • 0 in reply to McKenna Strambi
    TI__Genius 15150 points

    Hi McKenna,

    I do not recommend designing for a condition where the absolute maximum ratings are expected to be exceeded under any circumstances. This device has not been characterized for when the input voltage exceeds the absolute maximum rating.

    Under a condition where the voltage might exceed the absolute max rating, the input current should be sufficiently limited. It is generally recommended not to exceed 1mA input current to ensure the longevity of the device.

    Regards,
    Joel

  • 0 in reply to Joel Meraz
    TI__Intellectual 1530 points

    Hi Joel,

    In our application the input current to the ADC is much less than 1mA. It is ~2uA. Would we be able to get away with 0.2V over the absolute maximum rating in this condition?

    Having 3.8V on a 3.3V ADC input was not part of the plan, it is a corner case condition. We use the ADC to measure the USB cc pin voltage. We recently found out that if the USB C cable is slowly inserted from an angle, one cc pin will get in contact before the other cc pin, which triggers the USB interface from our side to release the pull down resistor on the latter cc pin, causing it to reach 3.8V once it gets in contact with the host side eventually.

    There is no way to change to a different chip in our design stage currently. We can avoid this over voltage situation by adding a Zener diode with a rework, but if we get your blessing for injecting 2uA @ 0.2V above the absolute maximum rating, then no rework. 

    Thanks!

    McKenna

  • +1 in reply to McKenna Strambi
    TI__Genius 15150 points

    Hi McKenna,

    I would not expect currents under 1mA to cause any long-term issues or damage the device. It should be okay considering this is a corner case that will rarely occur, and if it does occur, current is very small.

    Regards,
    Joel