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7.4.3 Bidirectional Mode (INA2191 Only)

The INA2191 is a dual channel bidirectional current-sense amplifier 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.

VOUT

1.7 V to 5.5 V

IN±

IN+

OUT

Bus Voltage

up to 40 V

RSENSE

Load

ENABLE

GND

CBYPASS

0.1 µF

INA2191 (½)

Capacitively

Coupled

Amplifier

REF

Reference

Voltage

ISENSE

Figure 7-6. Bidirectional Application

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

shown in Figure 7-6. 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

VS/2 for equal signal range in both current directions. In some cases, VREF is set at a voltage other than VS/2,

like 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–) times gain (plus VREF for INA2191) exceeds the voltage swing

specification, the INAx191 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 INAx191

returns to the expected value approximately 40 µs after the fault condition is removed. When the differential

voltage exceeds approximately 300 mV, the differential input impedance reduces to 3.3 kΩ, and results in a rapid

increase in bias currents as the differential voltage increases. A 3.3-kΩ resistance exists between IN+ and IN–

during a differential overload condition; therefore, currents flowing into the IN+ pin flow out of the IN– pin. An

increase in bias currents during a input differential overload occurs even with the device is powered down. Input

differential overloads less than the absolute maximum voltage rating do not damage the device or result in an

output inversion.

7.4.5 Shutdown

The INAx191 features an active-high ENABLE pin(s) that shuts down the device when pulled to ground. When

the device is shut down, the quiescent current is reduced to 10 nA per channel (typical), the input bias currents

are further reduced, and the disabled output goes to a high-impedance state. When disabled, the low quiescent

and input currents extend the battery lifetime when the current measurement is not needed. When the ENABLE

pin is driven above the enable threshold voltage, the device turns back on. When enabled, the typical output

settling time is 130 µs.

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INA191, INA2191

SLYS020B – FEBRUARY 2019 – REVISED FEBRUARY 2021

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