INA190 datasheet(14/48 Pages) TI2

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OUT

LOAD

SENSE

REF

GAIN

INA190

SBOS863D – MARCH 2018 – REVISED NOVEMBER 2019

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7.3 Feature Description

7.3.1 Precision Current Measurement

The INA190 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 INA190 is less than

15 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 INA190 is specified between 0.2% and 0.4% of the actual value, depending on

the gain option. 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 INA190 is different from many current-sense amplifiers because this device offers very low input bias

current. The low input bias current of the INA190 has three primary benefits.

The first benefit is the reduction of the current consumed by the device in both the enabled and disabled states.

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 INA190 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 INA190.

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 INA190 is only 48 µA (typ), 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 INA190 features an enable pin that turns off the device until needed. When in

the disabled state, the INA190 typically draws 10 nA of total supply current.

7.3.4 Bidirectional Current Monitoring

INA190 devices 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. The output voltage of the current-sense amplifier is shown in Equation 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.

(1)

INA190 Datasheet(PDF) 14 Page - Texas Instruments

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