VOUT

RESET

ALERT

IN+

IN±

VS+

GND

CMPIN

CMPREF

10 k:

RPULL-UP

+

±

0 V to 26 V

+

±

G = 20, 50,

100, 200

ADC

GPIO

GPIO

R1

R2

Microcontroller

5 V

2.7 V to 5.5 V

RSENSE

Load

INA381

13

INA381

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SBOS848B – DECEMBER 2017 – REVISED OCTOBER 2019

Product Folder Links: INA381

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7 Detailed Description

7.1 Overview

The INA381 is a zero-drift topology, current-sensing amplifier with an integrated comparator that can be used in

both low-side and high-side current-sensing and protection applications. This specially designed, current-sensing

amplifier accurately measures voltages developed across current-sensing resistors (also known as current-shunt

resistors) on common-mode voltages that far exceed the supply voltage powering the device. Current can be

measured on input voltage rails as high as 26 V, and the device can be powered from supply voltages as low as

2.7 V. The device can also withstand the full 26-V common-mode voltage at the input pins when the supply

voltage is removed without causing damage.

The zero-drift topology enables high-precision measurements with maximum input offset voltages as low as

150 µV, and a temperature contribution of only 1 µV/°C over the full temperature range of –40°C to +125°C. The

low total offset voltage of the INA381 enables the use of smaller current-sense resistor values, and allows for

more efficient system operation without sacrificing measurement accuracy due to the smaller input signal.

The device uses a reference input that simplifies setting the corresponding current threshold level to use for out-

of-range comparison. Combining the precision measurement of the current-sense amplifier and the onboard

comparator enables an all-in-one overcurrent detection device. This combination creates a highly-accurate

design that quickly detects out-of-range conditions, and allows the system to take corrective actions to prevent

potential component or system-wide damage.

7.2 Functional Block Diagram