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INA226: two questions about the accuracy of INA226

Oliver Ou
Intellectual 2845 points
Part Number: INA226

Hi team,

Customer has some question about INA226, could you give some comments?  thanks.

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1.Is that OK if the voltage (Current Shunt Resistor) is from 0-1.082mV ?

   Can INA226 make sure the max shunt voltage gain error is 0.1% based on the application condition

2.Could you help to propose the way which can increase the accuracy ?

We have to consider the voltage droop among the shunt resistor due to low voltage output, so the current shunt resistor can not be too big.

  • 0
    TI__Mastermind 23935 points

    Hello Oliver,

    Thanks for reaching out on the forum.

    The minimum shunt voltage resolution is 2.5uV. Assuming your customer got an INA226 with a Vos equivalent to the max specification (10uV) and provided no load, the first 4 ADC shunt voltage register codes would correspond to the device input offset. With the knowledge of a no load output, you can then discern a minimum current that is greater than 2.5uV/Rshunt.

    As for your customer’s upper bound of 1.082 mV that is ~1.3% of the available measurement scale (.001082/(2.5E-6V))/(2^15). For better resolution, you should try to use more of the scale.

    Presuming the current your customer wants to measure across the shunt is at least an order of 10 greater than input bias current (10uA), then a shunt voltage of 0.001082 may be achievable for your customer.

    When your customer purchases our device it is guaranteed to be within 0.1% for 3.3VS, 12V VBus over the shunt voltage input range (-81.9175mV and 81.92mV).

    There is not a way to improve the gain error without choosing another part. However, your customer can mitigate changes in accuracy by not using input filter resistors or by at least limiting those resistors to below 10ohm.

    Other areas to minimize error would be providing the device with a stable supply and increasing the conversion time as well as increasing the averaging.