INA181 datasheet(21/62 Pages) TI2

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7.4.3 Bidirectional Mode

The INAx181 are bidirectional, current-sense amplifiers capable of measuring currents through a resistive shunt

in two directions. This bidirectional monitoring is common in applications that include charging and discharging

operations where the current flowing through the resistor can change directions.

Power Supply, VS

2.7 V to 5.5 V

CBYPASS

0.1 µF

Single-Channel

TI Device

Bus Voltage

±0.2 V to +26 V

RSENSE

GND

Load

IN±

IN+

REF

OUT

Output

Reference

Voltage

Figure 7-7. Bidirectional Application

The ability to measure this current flowing in both directions is enabled by applying a voltage to the REF pin, as

shown in Figure 7-7. The voltage applied to REF (VREF) sets the output state that corresponds to the zero-input

level state. The output then responds by increasing above VREF for positive differential signals (relative to

the IN– pin) and responds by decreasing below VREF for negative differential signals. This reference voltage

applied to the REF pin can be set anywhere between 0 V to VS. For bidirectional applications, VREF is typically

set at mid-scale for equal signal range in both current directions. In some cases, however, VREF is set at a

voltage other than mid-scale when the bidirectional current and corresponding output signal do not need to be

symmetrical.

7.4.4 Input Differential Overload

If the differential input voltage (VIN+ – VIN–) multiplied by the gain exceeds the voltage swing specification, the

INAx181 drives the output as close as possible to the positive supply or ground, and does not provide accurate

measurement of the differential input voltage. If this input overload occurs during normal circuit operation, then

reduce the value of the shunt resistor or use a lower-gain version with the chosen sense resistor to avoid this

mode of operation. If a differential overload occurs in a fault event, then the output of the INAx181 returns to the

expected value approximately 20 µs after the fault condition is removed.

When the INAx181 output is driven to either the supply rail or ground, increasing the differential input voltage

does not damage the device as long as the absolute maximum ratings are not surpassed. Following these

guidelines, the INAx181 output maintains polarity, and phase reversal does not occur.

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INA181, INA2181, INA4181

SBOS793H – APRIL 2017 – REVISED NOVEMBER 2023

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