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INA226 - Calculating current reading accuracy

Kawai
Guru 19785 points
Other Parts Discussed in Thread: INA226

Hi Team,

Could you please tell me how to calculate the current reading accuracy for INA226 ?

I understand there is ADC offset and input bias current data in the datasheet. However, user would choose the calibration register value and I am not quite sure how these setting would affect to the accuracy.

Best Regards,

Kawai

  • 0
    TI__Genius 15770 points
    Hi Kawai,

    The calibration register setting won't affect current accuracy, it only affects the resolution. The highest resolution for the Current Register (04h) can be obtained by using the smallest allowable Current_LSB based on the maximum expected current as shown in Equation 2 of the datasheet.

    The INA226 does not necessarily measure current. The device measures both the differential voltage applied between the IN+ and IN- input pins and the voltage applied to the VBUS pin. In order for the device to report both current, the user must program the resolution of the Current Register (04h) and the value of the shunt resistor present in the application to develop the differential voltage applied between the input pins. Basically, the device takes two measurements, shunt voltage and bus voltage. It then converts these measurements to current, based on the Calibration Register value ( 0.00512/Current_LSB * RSHUNT).

    Accuracy will depend on your shunt voltage accuracy, offset voltage, shunt voltage gain error, Ib, etc. Please refer to video series 4 to 13 of our training video series. It explain which errors needs to be considered. Also, special attention to video "Section 15" that talks about Current calculations.
    e2e.ti.com/.../467332