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ADS1114: I2C output

Ryo Akashi
Expert 8950 points
Part Number: ADS1114
Other Parts Discussed in Thread: PCA9306

Hello experts,

I got question about I2C output from customer.
1. ADS1114's I2C output circuit is open drain?
 
2. If we use VDD=5V, MCU power supply=3.3V, do we need level translator IC?
    ADS1114's VIH is larger than 0.7VDD, If VDD=5V, larger than 3.5V is needed. So, level translator is needed. Is it correct?
Thanks and best regards,
Ryo Akashi
  • 0
    TI__Guru* 92655 points

    Akashi-san,


    Thanks for the questions on the ADS1114. I'll just answer them in the order they were asked.

    1. Like other I2C devices, the ADS1114 has an open drain for SDA and SCL pins. These require pull-up resistors for communications.

    2. The level translator may be needed, but this depends on the MCU and on other devices on the bus. The specification that you showed in the last post indicates the high level can be pulled above AVDD and that the pins are tolerant to 5.5V. This is helpful the MCU has a 5V supply and the ADS1114 has a 3.3V supply. You could tie the pull-ups to 5V and the ADS1114 would be able to tolerate the high supply for the I2C lines.

    You could also tie the pull-ups to 5V if the ADS1114 runs off 5V and the MCU has 5V tolerant SDA and SCL line (you would need to check with the MCU). However, you also need to check with the other devices on the I2C bus and see if they were tolerant to 5V or are run off of 5V.

    However I would suspect that the system would require an I2C translator.


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Expert 8950 points

    Hello Joseph-san,

     

    Thank you very much for your kind advice and I’m very sorry for my late reply.

    I understand about I2C of ADS1114.

     

    Also, it would be needed level translator, so, I will check I2C level translator.

     

    Thanks and best regards,

    Ryo Akashi

  • 0 in reply to Ryo Akashi
    TI__Guru* 92655 points

    Akashi-san,

    If you're looking for an I2C level translator, we've often recommended the PCA9306. I'll close this post for now, but let me know if you have any other questions about the ADS1114.

    Joseph Wu