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INA250: How to calculate variability

Kaji@PAN
Mastermind 8010 points

Part Number: INA250

Hello,

I use TI WEB's Current sense amplifier error analysis to calculate the variability of INA250A2.
So I would like to ask you a question.
As a result calculated by the tool, in the case of 3.675A, Total Error was output as 1.408%.
(question 1)
In this case, how should I calculate the VOUT of INA250?
Does the following content match?

Since VOUT = ILOAD × GAIN + REF,
ILOAD x GAIN x 1.01408 ⇒ Device MAX variation
ILOAD x GAIN x 0.98592 ⇒ Device MIN variation

(Question 2)
Is the operating temperature of the tool the ambient temperature or the package temperature?

(Question 3)
Since this device has a built-in resistor, I don't think it is necessary to set the Ideal shunt resistor item, but is it correct?
In this case, is the resistance variation reflected in the Total Error?

Best regards,

  • +1
    TI__Mastermind 25665 points

    Kaji,

    Thanks for choosing TI! Please find answers to the above questions below:

    1) If the total error calculated is 1.01408%, then your equations above would be correct. For the INA250A2, the GAIN is given as 500mV/A, so for 3.675A as you've defined, the output variation would be 

    Vout, max = ILOAD*GAIN*(1+error) = 1.863V

    Vout, min = ILOAD*GAIN*(1-error) = 1.812V

    Keep in mind that the calculator only takes into account the following errors: Vos, CMRR, PSRR, Gain error, drift specs @Ta (for the temperature curve). This can be seen in the note on top of the calculator:

    Note that this will not take into account additional error sources, such as PCB contributions, so additional analysis may be required. This curve is intended simply to provide a quick look at potential performance for a given use case. 

    2) Ambient temperature. This value corresponds to the operating temperature given in the datasheet, and is used in the calculator for generating drift errors at the temperature specified by the user.

    3) The calculator follows a standard format for ease of implementation on ti.com, but for our integrated shunt products, the calculations are performed on the fixed value of the shunt given in the datasheet. You can see that by changing this value and updating the curve, there are no changes to the error observed in the curve.