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ina199 offset voltage

Luke Sun
Intellectual 1830 points

Other Parts Discussed in Thread: INA199, INA210

Hi team,

My customer has a question of INA199 offset voltage.

They found that the typ. and max. value of INA199 offset voltage has big difference. typ. is 5uV, but max is 150uV.

Why it has a so big difference? Simply because of device variation or some other reasons?

Thank you!

  • 0
    TI__Genius 15770 points
    Hi Luke,

    I will review and get back to you.

    Mayrim
  • 0
    TI__Genius 15770 points
    Hi Luke,

    It could be device variation. I am not able to find the distribution data of the INA199 but that 150uV was clearly present in some of the devices that were tested. I see the spec is general, same spec for all gains. For higher gains the maximum should be lower, that's my guess. I am making this assumption based on the way INA210 (similar device) specs.

    Regards,
  • 0 in reply to Mayrim Verdejo
    Prodigy 30 points
    Did you finally find the answer? I am also wondering about this.
  • 0 in reply to yan son
    TI__Genius 15770 points
    Hi Yan,

    As specified before, it is device variation. To accommodate for statistical variation in material and measurement, we have to spec the max limit with a Cpk greater than 2.0.
  • 0 in reply to Mayrim Verdejo
    Prodigy 90 points

    Hi,

    I would like further clarity on the INA199B1 Offset voltage specification.
    I am trying to establish conservative design limits over process & temperature for this part.

    Initial variation at 25degC:
        From what has been posted so far, and the information in the datasheet (rev G):

        Vos is specified as +/-5uV nominal / +/-150uV max, AT 25degC, RTI.
        The graph of Vos vs. temperature shows |dVos/dT| is < 5uV

        *** I assume the graph of Vos is also RTI

        So I take as my starting point:  Vos @ 25degC = +/-150uV RTI

    Over temperature:
        Datasheet specifies dVos/dT = 0.5uV/degC MAX, full operating temperature range.

        *** NOT specified, but I also assume that this figure is RTI.

        My application max design temperature is 85degC, 85-25=60, so,
        Vos can be 60*0.5 = 30uV higher, Max.
        (per my reading of the datasheet, at -45degC is the offset -60*0.5 = -30uV)

        So I have design corner values of:
            Vos @ 85degC (and process, etc) =  +/-180uV RTI
            Vos @ -45degC (and process, etc) =  +/-180uV RTI
        resulting in (B1 = gan 50)  Vos = 50*180uV = +/-9mV at the output in each case.

    Is this a correct and conservative design limit, or have I misunderstood the data?

    Kind regards,

    George Tzanatos.

  • 0 in reply to George Tzanatos52
    TI__Genius 15770 points

    Hi George,

    Your interpretation of the data is correct! 

    Sorry we missed your post. I did not receive notification as the original post was from 2016. For next time please create a new post and add the link of the post you are referring to so we make sure we do not miss your questions!