INA181

2.7 V to 5.5 V

Bus Voltage

±0.2 V to +26 V

GND

VS

Load

IN±

IN+

OUT

REF

+

±

0.1 µF

Copyright © 2017, Texas Instruments Incorporated

Output

16

INA181, INA2181

SBOS793A – APRIL 2017 – REVISED AUGUST 2017

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8.4 Device Functional Modes

8.4.1 Normal Mode

The INAx181 are in normal operation when the following conditions are met:

•

•

•

•

Rail Output Swing section).

During normal operation, the device produces an output voltage that is the gained-up representation of the

8.4.2 Unidirectional Mode

The device can be configured to monitor current flowing in one direction (unidirectional) or in both directions

(bidirectional) depending on how the REF pin is configured. The most common case is unidirectional where the

output is set to ground when no current is flowing by connecting the REF pin to ground, as shown in Figure 38.

When the current flows from the bus supply to the load, the input signal across IN+ to IN– increases, and causes

the output voltage at the OUT pin to increase.

Figure 38. Unidirectional Application

The linear range of the output stage is limited by how close the output voltage can approach ground under zero

input conditions. In unidirectional applications where measuring very low input currents is desirable, bias the REF

pin to a convenient value above 50 mV to get the output into the linear range of the device. To limit common-

mode rejection errors, buffer the reference voltage connected to the REF pin.

method results in the output voltage saturating at 200 mV less than the supply voltage when no differential input

signal is present. This method is similar to the output saturated low condition with no input signal when the REF

pin is connected to ground. The output voltage in this configuration only responds to negative currents that

develop negative differential input voltage relative to the device IN– pin. Under these conditions, when the

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