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ADS1115: Tolerance for 5v VDD and 3v3 I2C pullups

Steve Glowacki
Prodigy 40 points
Part Number: ADS1115

My project will be using the ADS1115 with four single-ended sensors needing 5Vref  and interfacing with an ESP32 running at 3v3.  Would it work to connect the I2C pullups to 3v3 between the two?

ADS1115

  • 0
    TI__Mastermind 24940 points

    Hello,

    I am not sure what you mean by "between the two"

    But the power supply, which determines the analog full scale is independent of the digital voltage. Thus you can use a 5V VDD and use a 3.3V pull up for the I2C communications.

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Prodigy 40 points

    Cynthia,

    I think you answered my question.  Between the two - was about the I2C connection.  

    Thank you Very much!

    Steve

  • 0 in reply to Steve Glowacki
    TI__Guru* 92655 points

    Steve,


    I'd like to point out something from the datasheet. In the electrical characteristics table, you'll find the digital pin levels for the I2C:



    For an input, to guarantee the input to be registered as a high, the level is 0.7*VDD. For a 5V supply this is 3.5V, so tying the pull-ups to 3.3V, you don't guarantee communications. With this specification there's probably some margin, and I would guess that it would likely work, but it's not a certainty.

    I would check to see if the microcontroller has digital inputs that are tolerant to 5V, that way, you could tie the pull-ups to the 5V supply instead of the 3.3V supply.

    If that's not the case, you may need to use some sort of I2C voltage level translator.


    Joseph Wu