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 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 V+. For bidirectional applications, VREF is typically set at

midscale for equal signal range in both current directions. In some cases, however, VREF is set at a voltage other

than midscale when the bidirectional current and corresponding output signal do not need to be symmetrical.

7.2.2.3 Application Curve

An example output response of a bidirectional configuration is shown in Figure 7-4. 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.

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SBOS437K – MAY 2008 – REVISED NOVEMBER 2023

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