7.3.2 Precise Low-Side Current Sensing

When used in low-side current-sensing applications, the offset voltage of the INA381 is less than 150 µV. The low offset performance of the device has several benefits. First, the low offset allows the device to be used in applications that must measure current over a wide dynamic range. In this case, the low offset voltage improves accuracy when the sense currents are on the low end of the measurement range. Another advantage of low offset voltage is the ability to sense lower voltage drops across the sense resistor accurately, thus allowing for a lower-value shunt resistor. Lower-value shunt resistors reduce power loss in the current-sense circuit, and help improve the power efficiency of the end application.

The gain error of the INA381 is specified to be within 1% of the actual value. As the sensed voltage becomes much larger than the offset voltage, this gain error becomes the dominant source of error in the current-sense measurement.