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REF5020-EP: "Initial Accuracy Over Temperature" -VS- "Output Voltage Temperature Drift" & Long-Term-Drift

WolfHort
Prodigy 80 points
Part Number: REF5020-EP

Hello,

I am using the REF5020-EP part in a precision sensor design and I noticed that the datasheet calls out an initial accuracy, initial accuracy over temperature, and temperature drift coefficient.

  • Initial Accuracy: +/-0.05%
  • Initial Accuracy (Over Temperature): +/-0.08%
  • dVout/dT : 5ppm/C

Should the initial accuracy over temperature and the dVout/dT be accounted for separately in any accuracy budgets?

Or does the ppm/C added onto the base initial accuracy "encompass" the initial accuracy over temperature number?

...

Also -- I did not see any long-term stability ppm values in the REF50xx-EP datasheet... Are the numbers listed in the REF50xx base datasheet (not EP part) a good set to use for these parts as well?

  • 0
    TI__Genius 16021 points

    Hello,

    Correct. Temperature drift needs to be added to the initial accuracy. 

    Long term drift should be same as non-EP device. 


    Hope that helps!

  • 0 in reply to Masoud Beheshti61
    Prodigy 80 points

    Understood -- but does the ppm/C already account for the temperature drift from initial accuracy and thus the "Initial Accuracy Over Temperature" is redundant?

    Say for example that I am operating at 80 deg C and only accounting for temperature variation + initial accuracy..

    Would it be appropriate to use --

    0.05% + 5ppm/C * (80-25) 

    Or

    0.08% + 5ppm/C * (80-25)

    Or something in between?

    Basically -- Does the 0.05% + ppm/C overlap with the 0.08% listed "Over Temperature" ?

  • 0 in reply to WolfHort
    TI__Genius 16021 points

    Hello,

    Tempco and initial accuracy are independent specs.

    Initial accuracy is "out of the box" spec. if you are starting at 25C, then you take the 0.05% tolerance and add tempco to calculate total accuracy. However, worst case accuracy would be initial accuracy over temp (0.08%) plus tempco.

    Hope that helps.

    Thanks.

  • 0 in reply to Masoud Beheshti61
    Prodigy 80 points

    Masoud,

    So I am probably just confused... But I am struggling to understand your most recent reply.

    If I start at 25C and add tempco and that does in fact get me total accuracy at a given temperature... Then why is the "initial accuracy over temp" relevant?

    And it also doesn't say what temperature it is relevant at... An additional 0.03% hit is fairly significant for our application so I want to be confident it isn't overly conservative to apply it as well.

    Basically my question really boils down to:

    If I want to assess the accuracy at 80 deg C -- Can I just do 0.05% (initial accuracy) + 5ppm/C*(80C - 25C) to bound the total accuracy?

    Your above reply seems to suggest "yes" in the first sentence... but then contradicts that in the follow up sentence? Unless I am just confused.

    Eric

  • +1 in reply to WolfHort
    TI__Genius 16021 points

    Sorry about any confusion. Let me re-state:

    Tempco and initial accuracy are independent specs.

    Initial accuracy is "out of the box" spec. if you are starting at 25C, then you take the 0.05% tolerance and add tempco to calculate total accuracy.

    Thank you.