INA186 datasheet(13/44 Pages) TI2

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7.4 Device Functional Modes

7.4.1 Normal Operation

The INA186-Q1 is in normal operation when the following conditions are met:

• The power-supply voltage (VS) is between 1.7 V and 5.5 V.

• The common-mode voltage (VCM) is within the specified range of –0.2 V to +40 V.

• The maximum differential input signal times the gain plus VREF is less than the positive swing voltage VSP.

• The ENABLE pin is driven or connected to VS.

• The minimum differential input signal times the gain plus VREF is greater than the zero load swing to GND,

VZL (see Rail-to-Rail Output Swing).

For devices that do not feature a REF pin that value for VREF will be zero. 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. Figure 7-2 shows the device operating in

unidirectional mode where the output is near ground when no current is flowing. 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.

VOUT

1.7 V to 5.5 V

IN±

IN+

OUT

Bus Voltage

up to 40 V

RSENSE

Load

Capacitively

Coupled

Amplifier

INA186-Q1

REF

GND

ISENSE

CBYPASS

0.1 µF

Figure 7-2. 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-Q1 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.

A less-frequently used output biasing method is to connect the REF pin to the power-supply voltage, VS. This

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

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INA186-Q1

SBOS386B – MAY 2019 – REVISED MARCH 2022

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