9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

The INA241x amplifies the voltage developed across a current-sensing resistor as current flows through

the resistor to the load. The wide input common-mode voltage range and high common-mode rejection of

the INA241x make it usable over a wide range of voltage rails while still maintaining an accurate current

measurement.

9.1.1 RSENSE and Device Gain Selection

The accuracy of any current-sense amplifier is maximized by choosing the largest current-sense resistor value

possible. A larger value sense resistor maximizes the differential input signal for a given amount of current

flow and reduces the error contribution of the offset voltage. However, there are practical limits as to how

large the current-sense resistor value can be in a given application because of the physical dimensions of the

package, package construction, and maximum power dissipation. Equation 2 gives the maximum value for the

current-sense resistor for a given power dissipation budget:

MAX

SENSE

2

MAX

PD

R

I

(2)

where:

• PDMAX is the maximum allowable power dissipation in RSENSE.

• IMAX is the maximum current that will flow through RSENSE.

An additional limitation on the size of the current-sense resistor and device gain is due to the power-supply

voltage, VS, and device swing-to-rail limitations. To make sure that the current-sense signal is properly passed

to the output, both positive and negative output swing limitations must be examined. Equation 3 provides the

maximum values of RSENSE and GAIN to keep the device from exceeding the positive swing limitation.

I

MAX

ª RSENSE ª *$,1 < VSP

(3)

where:

• IMAX is the maximum current that will flow through RSENSE.

• GAIN is the gain of the current-sense amplifier.

• VSP is the positive output swing of the device as specified in the Specifications.

To avoid positive output swing limitations when selecting the value of RSENSE, there is always a trade-off

between the value of the sense resistor and the gain of the device under consideration. If the sense resistor

selected for the maximum power dissipation is too large, then it is possible to select a lower gain device to avoid

positive swing limitations.

The negative swing limitation places a limit on how small the sense resistor value can be for a given application.

Equation 4 provides the limit on the minimum value of the sense resistor.

I

MIN

ª RSENSE ª *$,1 > VSN

(4)

where:

• IMIN is the minimum current that will flow through RSENSE.

INA241A, INA241B

SBOSA30A – MARCH 2022 – REVISED AUGUST 2022

www.ti.com

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