INA190 datasheet(23/37 Pages) TI

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As the voltage drop across the sense resistor (VSENSE) increases, the amount of voltage dropped across the

input filter resistors (RF) also increases. The increased voltage drop results in additional gain error. Use Equation

5 to calculate the error caused by these resistors.

DIFF

SENSE

DIFF

Error(%)

100

2 R

(5)

where:

• RDIFF is the differential input impedance.

• RF is the added value of the series filter resistance.

The input stage of the INA190-EP uses a capacitive feedback amplifier topology to achieve high dc precision. As

a result, periodic high-frequency shunt voltage (or current) transients of significant amplitude (10 mV or greater)

and duration (hundreds of nanoseconds or greater) may be amplified by the INA190-EP, even though the

transients are greater than the device bandwidth. Use a differential input filter in these applications to minimize

disturbances at the INA190-EP output.

The high input impedance and low bias current of the INA190-EP provide flexibility in the input filter design

without impacting the accuracy of current measurement. For example, set RF = 100 Ω and CF = 22 nF to

achieve a low-pass filter corner frequency of 36.2 kHz. These filter values significantly attenuate most unwanted

high-frequency signals at the input without severely impacting the current-sensing bandwidth or precision. If a

lower corner frequency is desired, increase the value of CF.

Filtering the input filters out differential noise across the sense resistor. If high-frequency, common-mode noise

is a concern, add an RC filter from the OUT pin to ground. The RC filter helps filter out both differential and

common-mode noise, as well as internally generated noise from the device. The value for the resistance of the

RC filter is limited by the impedance of the load. Any current drawn by the load manifests as an external voltage

drop from the INA190-EP OUT pin to the load input. To select the optimal values for the output filter, use Figure

6-33 and see the Closed-Loop Analysis of Load-Induced Amplifier Stability Issues Using ZOUT application report

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INA190-EP

SBOSA74 – MAY 2022

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INA190 Datasheet(PDF) 23 Page - Texas Instruments