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ADS1000 5v for VDD, 3.3V for I2c

Lucifer
Expert 2600 points
Other Parts Discussed in Thread: ADS1000, PCA9306

Dear Sir,

Can I use ADS1000 for 5V VDD and 3.3V tied to I2C? Thanks.

  • 0
    TI__Guru* 92715 points
    Passerby,


    The VIH minimum is 0.7xVDD. That means for a 5V supply, the part is guaranteed to recognize a high level at 3.5V, with the pull up resistors at 3.3V, it is lower than the minimum. Having a direct connection might work, but it is not guaranteed, and I would not recommend it.

    If you need to connect I2C devices that use different voltages, you should use some sort of level shifting for the communications. I would recommend the PCA9306 to connect the microcontroller to the ADC.

    www.ti.com/.../pca9306


    Joseph Wu
  • 0 in reply to Joseph Wu
    Expert 2600 points

    Dear Joseph,

    if we don't wnat to use I2C level shift, does TI have another ADC can meet this requiremnet? Thanks.

  • 0 in reply to Lucifer
    TI__Guru* 92715 points
    Passerby,


    Typical VIL level is 0.7xAVDD, so it is generally not possible to have it work so that the input from the microcontroller work off of 3.3V pull-ups.

    The only way to do this without some sort of level shift would be to have the pull-up set to the 5V level and have a microcontroller with a 5V tolerant input.


    Joseph Wu