+

±

REF2

REF1

VS

GND

OUT

VS

IN+

IN±

+

±

REF2

REF1

VS

GND

OUT

VS

IN+

IN±

13

INA240

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SBOS662A – JULY 2016 – REVISED OCTOBER 2016

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Device Functional Modes (continued)

8.4.2 Reference Pin Connections for Unidirectional Current Measurements

Unidirectional operation allows current measurements through a resistive shunt in one direction. For

unidirectional operation, connect the device reference pins together and then to the negative rail (see the Ground

Referenced Output section) or the positive rail (see the VS Referenced Output section). The required differential

input polarity depends on the output voltage setting. The amplifier output moves away from the referenced rail

proportional to the current passing through the external shunt resistor. If the amplifier reference pins are

connected to the positive rail, then the input polarity must be negative to move the amplifier output down

(towards ground). If the amplifier reference pins are connected at ground, then the input polarity must be positive

to move the amplifier output up (towards supply).

The following sections describe how to configure the output for unidirectional operation cases.

8.4.2.1 Ground Referenced Output

When using the INA240 in a unidirectional mode with a ground referenced output, both reference inputs are

connected to ground; this configuration takes the output to ground when there is a 0-V differential at the input (as

Figure 25 shows).

Figure 25. Ground Referenced Output

8.4.2.2 VS Referenced Output

Unidirectional mode with a VS referenced output is configured by connecting both reference pins to the positive

supply. Use this configuration for circuits that require power-up and stabilization of the amplifier output signal and

other control circuitry before power is applied to the load (as shown in Figure 26).

Figure 26. VS Referenced Output