1.7 V to 5.5 V

IN±

IN+

VS

OUT

+

±

Bus Voltage

up to 40 V

Load

Capacitively

Coupled

Amplifier

INA186

REF

GND

0.1 µF

13

INA186

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SBOS318 – APRIL 2019

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7.4 Device Functional Modes

7.4.1 Normal Operation

The INA186 is in normal operation when the following conditions are met:

•

•

•

•

(see the Rail-to-Rail Output Swing section).

During normal operation, this device produces an output voltage that is the amplified representation of the

difference voltage from IN+ to IN– plus the voltage applied to the REF pin.

7.4.2 Unidirectional Mode

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

(bidirectional) depending on how the REF pin is connected. 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 21.

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

the output voltage at the OUT pin to increase.

Figure 21. Typical Unidirectional Application

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

input conditions. The zero current output voltage of the INA186 is very small and for most unidirectional

applications the REF pin is simply grounded. However, if the measured current multiplied by the current sense

resistor and device gain is less than the zero current output voltage, then bias the REF pin to a convenient value

above the zero current output voltage 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 40 mV less than the supply voltage when no differential input

voltage is present. This method is similar to the output saturated low condition with no differential input voltage

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

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

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