7.2.2 Bidirectional Operation

-

Reference

Voltage

CBYPASS

0.1 µF

Output

-

+

IN-

IN+

GND

V+

OUT

REF

Power Supply

Bus Supply

Load

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Figure 7-3. Bidirectional Application Schematic

7.2.2.1 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.

7.2.2.2 Detailed Design Procedure

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

shown in Figure 7-3. 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 the VREF value for positive differential signals (relative

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

voltage applied to the REF pin can be set anywhere between 0 V to V+. For bidirectional applications, the VREF

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

the VREF value is set at a voltage other than mid-scale when the bidirectional current and corresponding output

signal are note required to be symmetrical.

7.2.2.3 Application Curve

Figure 7-4 shows an example output response of a bidirectional configuration. With the REF pin connected to

a reference voltage, 2.5 V in this case, the output voltage is biased upwards by this reference level. The output

rises above the reference voltage for positive differential input signals and falls below the reference voltage for

negative differential input signals.

Time (500 µs/div)

V

OUT

V

REF

0 V

Figure 7-4. Bidirectional Application Output Response

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