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INA237: VIL threshold confirmation

Jaden Yue
Expert 5125 points
Part Number: INA237
Other Parts Discussed in Thread: INA327, INA226,

Hi Team,

From the datasheet of VIL, can I understand the maximum 0.4V means the threshold that regard as low will not exceed 0.4V? For example, if the VIL = 0.5V, we cannot regard it as signal low? Now customer measured the I2C DAT low voltage level is 511.236 mV. Does it mean it is out of our range?

Best Regards,

Jaden Yue

  • 0
    Guru 268160 points

    The input voltage must be 0.4 V or lower for it to be guaranteed to be read as low. The actual switching threshold will be higher, near 0.8 V, but there is no guarantee. (The 0.4 V limit does not conform to the I²C specification, but allows to use an I²C bus running at a supply voltage lower than the INA327's VS.)

    Would it be possible to use weaker pull-up resistors? Or are you using an I²C buffer with a voltage offset?

  • 0
    TI__Mastermind 20545 points

    Hello Jaden,

    Per Clemens comment, 0.4V or lower is where the signal is guaranteed to register as low. So, with 511.236 mV a low reading is not guaranteed. I recommend making adjustments to get this below 0.4V. Both of Clemens suggestions could work, also, I've seen before that sometimes there are MCU settings that allow different levels of sink current, and increasing the current sinking capability may help as well (for the clock or other signals driven by the MCU).

    Regards,

    Mitch

  • 0 in reply to Mitch M
    TI__Expert 5125 points

    Hi Mitch,

    I2C buffer is not used in design.

    Because some boards are still in use, it is inconvenient to adjust the pull-up resistor. We will try again.

    Generally, the I2C signal spec is low level of 0.8-0.99V,

    Why does your I2C have a strict requirement of less than 0.4V?

    Is there any special treatment on the internal chip design?

    Best Regards,

    Jaden Yue

  • 0 in reply to Jaden Yue
    Guru 268160 points

    These thresholds are designed for an 1.8 V I²C bus.

    A low level of 0.5 V is likely to work, but this is not guaranteed.

  • +1 in reply to Jaden Yue
    TI__Mastermind 20545 points

    Hey Jaden,

    Since the datasheet says 0.4V max, that is what I recommend designing to. If you absolutely cannot achieve that, then you may be interested in the INA226, which has a higher VIL (based on VS). This device is footprint compatible with the INA237.

    Regards,

    Mitch