INA191 datasheet(13/22 Pages) TI1

13 / 22 page

DIFF

SENSE

DIFF

Error(%)

100

2 R

INA191

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SLYS020 – FEBRUARY 2019

Product Folder Links: INA191

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Application Information (continued)

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. The error caused

by these resistors is calculated by the resistor divider equation shown in Equation 4.

where:

•

RDIFF is the differential input impedance.

•

RF is the added value of the series filter resistance.

(4)

An additional factor to consider when increasing the value of RF is the potential for increased output noise

because of the pulse current generated by the internal chopping of the input capacitor network. Because of the

pulse current, do not use values of RF greater than 1 kΩ. The advantages of the lower corner frequency of the

input filter is overcome by the additional noise caused by the internal capacitor chopping. If additional filtering is

needed, increase the value of CF.

To achieve best performance in applications with periodic high-frequency currents that are greater than the

device bandwidth, apply an input filter to attenuate differential current noise. Use a 100-Ω resistor for RF and a

22-nF capacitor for CF to achieve a low-pass filter corner frequency of 36.2 kHz. This result does not severely

impact the current-sensing bandwidth, but does filter out most high-frequency signals. If a lower corner frequency

is desired, increase the value of CF.

If high-frequency, common-mode noise is a concern, add an RC filter from the OUT pin to ground. 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 INA191 OUT pin to the load input.

INA191 датащи(PDF) 13 Page - Texas Instruments