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ADC081C027: I2C input characteristics - operation at the wrong rail

Lenio Cacula
Genius 16300 points
Part Number: ADC081C027

My customer is trying to understand the exposure of a design mistake in which the supply for the ADC081C027 is 5V, but the I2C lines, with 4.75kΩ pullup resistors, are connected to 3.3V. Boards have been working, despite the fact the datasheet requires 0.7xVA (3.5V in this application) as the minimum voltage for SCL and SDA. Since these characteristics are AOQL and not typical values, can you help us making a determination of percentage of parts expected to fail in the field?

Thank you!

  • +1
    TI__Guru 62975 points

    Hi Lenio,

    First, we'd like to recommend the customer resolve the issue such that they're not going to production with a below-minimum voltage limit Vih level.  That said, the 0.7xVa minimum specified voltage level is supported over the full temperature range and if the customer is testing at, or near, room temperatures then there are likely a good percentage of units that may work fine.  Over the full temperature range, and if the +3.3V supply sags down by a few hundred mV, many devices will likely not make it through as the specification indicates.

    Even if we produced an overall guess on how many units may make it through at 25C, it would not be possible to predict how many units the customer could receive that wouldn't work.  This is because they will likely get units from a single date code and if that date code operates close to the specified limit, then all of them could have issues. Similarly for other runs all units may work. 

    The variations in date codes would not be noticed if the products were operated within their specified supply limits where they are optimized to run.