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ADS7830: ADS7830 pull-up supply on SDA and ACL

JB63
Prodigy 230 points
Part Number: ADS7830


Do the pull-ups on the SCL and SDA lines always have to be tied to VDD for the part? 

For example, would it be allowed to power the part at 5V and pullup SDA and SCL to 3.3V?

  • 0
    TI__Intellectual 1205 points
    Hello!

    The I2C interface allows the flexibility to connect devices together from different logic families.
    This is an industry standard protocol, so there is plenty of information on the internet.
    To make a long story short, yes; you can power up a device at 5V and pull the SDA and SCL up to 3.3V.
    In most cases (check your datasheets to be sure), you can also go the other way, powering up your device to 3.3V and pulling the I2C lines up to 5V.
    The pullup resistor on an I2C line is the only thing that pulls the voltage high, so the speed of your bus is limited by the resistors working against the capacitance on the bus, as well as the I2C protocol (such as standard, fast, or high-speed) that you have selected and your devices support.

    This is a very general explanation, but I hope it helps.
  • 0 in reply to Bryan McKay
    Prodigy 230 points
    Hi Bryan,
    Thank you for the response.
    So then what would be the threshold levels for the SCL and SDA lines? I thought these would be related to the Vdd of the particular device. For example, in the ADS7830 data sheet under Logic Levels, it specifies a logic-1 as between Vddx0.7 to Vdd+0.5V.
    Thanks, John
  • 0 in reply to JB63
    TI__Intellectual 1205 points
    According to the Absolute Maximum table of the ADS7830 datasheet, Vdd can go as high as 6V, so the supply range itself can allow you to cover your logic level requirements. This datasheet has different spec tables for different supply ranges. There is one with the supply at 2.7V, and another with the supply at 5V.