input signal increases negatively, the output voltage moves downward from the saturated supply voltage. The

voltage applied to the REF pin must not exceed the device supply voltage.

8.2.1.3 Application Curve

An example output response of a unidirectional configuration is shown in Figure 8-2. With the REF pin

connected directly to ground, the output voltage is biased to this zero output level. The output rises above

the reference voltage for positive differential input signals but cannot fall below the reference voltage for negative

differential input signals because of the grounded reference voltage.

Time (500 µs /div)

Output

VREF

C001

0V

Figure 8-2. Unidirectional Application Output Response

8.2.2 Bidirectional Operation

-

Reference

Voltage

CBYPASS

0.1 µF

Output

-

+

IN-

IN+

GND

V+

OUT

REF

Power Supply

Bus Supply

Load

Copyright © 2017, Texas Instruments Incorporated

Figure 8-3. Bidirectional Application Schematic

8.2.2.1 Design Requirements

The device is a 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 flow-through resistor can change directions.

8.2.2.2 Detailed Design Procedure

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

see Figure 8-3. The voltage applied to REF (VREF) sets the output state that corresponds to the zero-input level

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INA199

SBOS469H – APRIL 2009 – REVISED OCTOBER 2023

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