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DAC8551: Question about INL and Relative Accuracy

Marius Isenmann
Prodigy 10 points
Part Number: DAC8551

Hello together,

we are wondering about some data information of DAC8551ID / DAC8551IA and DAC8551-Q1.
In the datasheet we did not find any information about the INL, but only about a "relative accuracy".
We wondered what the last value might be. We thought this is the total error, which consists of a gain error, an offset error and a nonlinearity error. 
What we do not know: How large is the INL, that is the error we can't calibrate.

In the datasheets we will only find some graphics on page 22 where a typical INL is specified. The "relative accuracy" of DAC8551ID is better then the "accuracy" of DAC8551IA.

Question 1: How large is the INL of DAC8551ID, DAC8551IA and DAC8551-Q1?
Question 2: If the INL is identically, can we assume DAC8551ID has a larger error in gain and offset?
Question 3: In parametric table, the DAC8551ID/IA and DAC8551-Q1 differ in their INL, in parametric table specified by 8 LSB and 16 LSB. We could not find any difference in the datasheet?

Thank you very much for any help.

Marius Isenmann

  • 0
    TI__Mastermind 30658 points

    Hi Marius,

    The INL is given as the relative accuracy in the datasheet. There was a datasheet revision for the DAC8551 that changed the relative accuracy from 8LSB to 12LSB max. The 8LSB in the parametric search might not have been updated with the revision. The DAC8551A and DAC8551-Q1 both have a max relative accuracy of 16LSB. 

    DAC8551 and DAC8551A:

    DAC8551-Q1:

    The offset and gain errors are also given in the datasheet. It looks like the offset error for the DAC8551 and DAC8551A are the same. The DAC8551A has a slightly larger max value for the gain error. 

    Best,

    Katlynne Jones

  • 0
    Prodigy 10 points

    Hi Katlynne,

    thank you very much for the quick answer.
    I tried to find a definition of the "relative accuracy", but couldn't find a good one.

    I could find only one: "Relative accuracy error (ADC/DAC) is the total unadjusted error/ absolute accuracy error expressed as a relative value."
    "The total unadjusted error [...] includes all contributions from offset error, gain error, linearity error, and the inherent quantization error."

    If I follow this definition, the "relative accuracy" consists of the "INL" error, but it is not the same.
    Are you sure, it is the same? So why isn't written INL there?

    Sorry that I ask nearly the same again.

    Marius Isenmann

  • +1 in reply to Marius Isenmann
    TI__Guru 53283 points

    Hi Marius,

    TI used to use the term "relative accuracy" for INL.  You can see that in the older revision of the DAC8551 (not that this datasheet has been revised and is not valid any longer, I only share this for clarity) we show 8LSB max for "relative accuracy".  The front page was not updated when we expanded the specification to 16LSB.  I will notify our system's team that the front page needs to be updated.

    slas429.pdf

    Many thanks,

    Paul