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Original question:

INA190: Sensitivity of the current sensor

INA190: Vout at zero input current

Kelvin Le THS
Expert 7855 points
Part Number: INA190


Hi,

My application measurement range is from 10mA to 5A with a 10mohm sense resistor.  Vcm = 12V. 

I'm using GND as the INA reference for unidirectional sensing.

The ADC Vref = 1.8V.

The INA190A1 specifies a 3mV (max) at zero input current, which translates to a 12mA error at zero input current given 25V/V gain and 10mohm shunt.

Should I treat this 3mV negative rail headroom as an offset error or a noise floor?  If my sense current is 12mA, will the INA Vout be 6mV (worst case) or 3mV?

Would you recommend using GND as a reference or should I offset the output with a 100mV Vref instead to avoid the negative rail.  This INA 100mV Vref will be generated with the 1.8V ADC reference for ratiometric measurement.  Please advise.

-Kelvin 

  • 0
    TI__Mastermind 34640 points

    Hi Kevin,

    The swing spec is the (worst case) output low voltage level. Therefore if the input current is 12mA or lower, the output may not be any lower than 3mV and you won’t be able to tell the true current magnitude based on the output voltage.

    It is not an offset. Its effect is similar to noise floor in that it imposes a limit on the smallest input signal.

    If you want to resolve current lower than 12mA, then offsetting output with 100mV is a better choice.

    Regards, Guang