IN+

IN-

-0.2 V to 26 V

Power Supply

IN+

IN-

High-Side Sensing

is bus-voltage dependent.

Low-Side Sensing

is always near ground and is

isolated from bus-voltage spikes.

GND

Load

8

INA381

SBOS848 – DECEMBER 2017

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7.3 Feature Description

7.3.1 Wide Input Common-Mode Voltage Range

The INA381 supports input common-mode voltages from –0.2 V to 26 V. Because of the internal topology, the

range of 2.7 V to 5.5 V. As Figure 1 shows, the ability to operate with common-mode voltages greater or less

Figure 1. High-Side and Low-Side Current Sensing

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 INA381 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 improves the

accuracy when the sense currents are on the low end of the measurement range. Another advantage of low

offset is the ability to sense lower voltage drop 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.