INA186 datasheet(12/45 Pages) TI2

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7.3 Feature Description

7.3.1 Precision Current Measurement

The INA186 allows for accurate current measurements over a wide dynamic range. The high accuracy of the

device is attributable to the low gain error and offset specifications. The offset voltage of the INA186 is less than

±50 µV. In this case, the low offset improves the accuracy at light loads when VIN+ approaches VIN–. Another

advantage of low offset is the ability to use a lower-value shunt resistor that reduces the power loss in the

current-sense circuit, and improves the power efficiency of the end application.

The maximum gain error of the INA186 is specified at ±1%. As the sensed voltage becomes much larger than

the offset voltage, the gain error becomes the dominant source of error in the current-sense measurement.

When the device monitors currents near the full-scale output range, the total measurement error approaches the

value of the gain error.

7.3.2 Low Input Bias Current

The INA186 is different from many current-sense amplifiers because this device offers very low input bias

current. The low input bias current of the INA186 has three primary benefits.

The first benefit is the reduction of the current consumed by the device . Classical current-sense amplifier

topologies typically consume tens of microamps of current at the inputs. For these amplifiers, the input current is

the result of the resistor network that sets the gain and additional current to bias the input amplifier. To reduce

the bias current to near zero, the INA186 uses a capacitively coupled amplifier on the input stage, followed by a

difference amplifier on the output stage.

The second benefit of low bias current is the ability to use input filters to reject high-frequency noise before

the signal is amplified. In a traditional current-sense amplifier, the addition of input filters comes at the cost

of reduced accuracy. However, as a result of the low bias currents, input filters have little effect on the

measurement accuracy of the INA186.

The third benefit of low bias current is the ability to use a larger current-sense resistor. This ability allows the

device to accurately monitor currents as low as 1 µA.

7.3.3 Low Quiescent Current With Output Enable

The device features low quiescent current (IQ), while still providing sufficient small-signal bandwidth to be usable

in most applications. The quiescent current of the INA186 is only 48 µA (typical), while providing a small-signal

bandwidth of 35 kHz in a gain of 100. The low IQ and good bandwidth allow the device to be used in many

portable electronic systems without excessive drain on the battery. Because many applications only need to

periodically monitor current, the INA186 features an enable pin that turns off the device until needed. When in

the disabled state, the INA186 typically draws 10 nA of total supply current.

7.3.4 Bidirectional Current Monitoring

The INA186 devices that feature a REF pin can sense current flow through a sense resistor in both directions.

The bidirectional current-sensing capability is achieved by applying a voltage at the REF pin to offset the output

voltage. A positive differential voltage sensed at the inputs results in an output voltage that is greater than the

applied reference voltage. Likewise, a negative differential voltage at the inputs results in output voltage that

is less than the applied reference voltage. Use Equation 1 to calculate the output voltage of the current-sense

amplifier.

OUT

LOAD

SENSE

REF

GAIN

(1)

where

• ILOAD is the load current to be monitored.

• RSENSE is the current-sense resistor.

• GAIN is the gain option of the selected device.

• VREF is the voltage applied to the REF pin.

INA186

SBOS318B – APRIL 2019 – REVISED JULY 2021

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