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ADS7142: Minimum fall time requirement

Shota Mago
Expert 8880 points

Part Number: ADS7142

Hi team,

My customer considers to use the ADS7142 in Fast-Mode Plus. In timing characteristics, threre "Min"requirement for fall time.I understand this is based on the I2C standard, but could you explain the rationale behind it? Also, what are the potential risks if this requirement is not met?

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Best regards,

Shota Mago

  • +1
    TI__Mastermind 21520 points

    Hi Mago-san 

    Apologies for the late reply. Yes, the ADS7142 I2C timing characteristics are meant to conform to I2C standards. There is no significant risk of going below this minimum, due to I2C pins being open-drain buffer, the fall time will be limited by the pull-up resistors. 

    With DVDD = 3.6V, the minimum fall time is 20ns, but it is not necessarily the length of the fall time that we are concerned about, but the dV/dt on the I2C lines. If a controller drives the I2C lines with a push-pull driver rather than an open-drain driver, it is possible to see ringing on the lines, and this might cause the device to see false START/STOP conditions.

    As mentioned, provided the device has proper pull up resistors (typically from 1kΩ to 10kΩ), and the controller also conforms to I2C standard, any potential issues are of least concern. 

    Regards,
    Joel