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INA240-Q1: Total error calculation

Jeramie Bianchi
Expert 3315 points
Part Number: INA240-Q1
Other Parts Discussed in Thread: INA240

I'm working with a customer to calculate expected accuracy in the system per below schematic.

Based on this being mid-supply architecture and them planning to use 100V/V gain device with Imax = 8.1A. I've calculated the below. Can you please verify if this is correct?

Vdiff = 2.5V / 100 = 25mV (assumed Vout is Vs/2) - should i take into account input value not being 0V? (I saw 3V full scale being reference in table 8.1 in datasheet)

Rsense = 25mV / 8.1A = 3mOhm

Prsense = 197mW

Vsense = 8.1A * 3mOhm = 24.3mV

Error_VOS = 5uV / 24.3mV = 0.02%

Error_lin = 0.01%

Error_gain = 0.33%


Considering those, it seems that total error is dominated by gain error, so per total error equation in datasheet, the error is effectively gain error due to external resistors or 0.33%.

  • 0
    TI__Mastermind 26475 points

    Hello Jeramie,

    Yes the gain error will be dominated by the external resistors.  You also did not add the gain error of the INA240.  The 0.33% error is in addition to the gain error.  On the product page you can input these numbers except for series resistors to get the error.  We also have this tool for calculating error.  

    Current Sense Amplifier Comparison and Error Tool (Rev. D)

    This tool does use maximum not typical values.  Even with this you will most likely have a larger error with the Rshunt used will most be the major contributor unless they are spending the money for the very accurate resistor.  Also do they need the resistor filter at the input?  Could they filter the output?