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INA2180-Q1: current measurement accuracy

Ryan Wang
Expert 6380 points
Part Number: INA2180-Q1
Other Parts Discussed in Thread: CS-AMPLIFIER-ERROR-TOOL

Dear expert,

Customers want to use INA2180-Q1 for high side current measurement.

Current is from 1A~30A. Current sensor resistor is 3mohm. Battery voltage is 9-16V.  ADC is 0~5V range. 

For INA2180A2-Q1, 50Gain*3mohm*30A=4.5V<5V ADC range

"±500 μV (maximum) at VCM = 12 V", what's offset voltage for 16V(max battery voltage)? Let me assume it is 700uV

700+1μV/°C*(85C-25C)=760uV

For 3mohm resistor,  760uV/3mohm=250mA accuracy. 

Is my above calculation correct for INA2180A2-Q1?

And how to calculate accuracy considering Input bias current, power supply voltage (9V~16V), gain error?

Customer wants to know the worst case.

Thanks a lot

  • 0
    TI__Mastermind 29490 points

    Hello Ryan,

    We normally do not do worst case as the error are not all correlated and we normally use the RSS.  There are two calculators you can use. One is on the product page.  The other is also on the product page(CS-Amplifier-Error-Tool) in the design and development section.

    Here is some more detail. 

    https://training.ti.com/ti-precision-labs-current-sense-amplifiers-offset-error

    Vos = 500µV

    CMRR = (VCM_used - VCM_InDatashet) * 84dB (63.1µV/V) 

    For 16V  

    Vos @16V @Room = 500µV+ (16-12)*63.1µV = 752.4µV

    Vos @16V VCM @ 85C = 812.4µV would be worst case.  This calculation for drift is the same as yours above then adding to the one above.

    IB if there are 80µA which is much smaller than the the 250mA error you mentioned above.

    Power supply is limited to 2.7V to 5.5V.

    PSRR = (PS_used - PS_InDatasheet) * 40µV/V  *Power supply in datasheet = 5V.

    CS-AMPLIFIER-ERROR-TOOL — Current sense amplifier comparison and error tool