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ADS8321 Differential input - common mode voltage range vs Vref (fig 3 in datasheet sbas123b)

Other Parts Discussed in Thread: ADS8321

ADS8321 datasheet figure 3 is unclear. The low limit streches from -0.3V to about 0.95V according to the shadowed area, but the voltage indicated on the right says 1.95V. Which is correct?

  • Hello Kalle,

    Welcome to the E2E community.

    Sorry for taking so long to provide an answer. Last week, we were short handed and overlooked your post. We usually reply as soon as possible within a couple of days at the most.

    The graph is correct. The number in the right y-axis is incorrect. For full-scale swing and 2.5Vref, 1.95V is NOT the minimum common mode voltage.

    With a 2.5V reference, the common mode should be a value between 2.75V and 0.95V to allow full-scale inputs.

    To clarify, the following image shows three common mode cases (0.95V, 1.95V, and 2.75V) at 2.5Vref and full-scale inputs.


    Best regards,

  • Hi Kalle,

    The image had a little typo and I just corrected the previous post.

    Note that this doesn’t change the answer.

    0.95V is the minimum common mode with 2.5V ref and full input swing. As the image shows, the minimum voltage of the inputs is what limits the common mode to 0.95V.

    Best regards,