INA181 datasheet(17/34 Pages) TI1

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INA181

Power Supply, VS

2.7 V to 5.5 V

Bus Voltage

±0.2 V to +26 V

RSENSE

GND

Load

IN±

IN+

REF

CBYPASS

0.1 µF

OUT

Output

Reference

Voltage

INA181, INA2181

www.ti.com

SBOS793A – APRIL 2017 – REVISED AUGUST 2017

Product Folder Links: INA181 INA2181

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Device Functional Modes (continued)

8.4.3 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.

Figure 39. 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 39. 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.

8.4.4 Input Differential Overload

If the differential input voltage (VIN+ – VIN–) times gain exceeds the voltage swing specification, the INAx181 drive

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.

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