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 INA254 measures the voltage developed as current flows across the integrated low inductive current-

sensing resistor. The device provides reference pins to configure operation as either unidirectional or

bidirectional output swing. When using the INA254 for inline motor current sense or measuring current in an

H-bridge, the device is commonly configured for bidirectional operation.

9.1.1 Input Filtering

Note

Input filters are not required for accurate measurements using the INA254. For most accurate results,

do not use filters at the IN+ and IN– inputs. However, If filter components are used on the input of the

amplifier, follow the guidelines in this section to minimize effects on performance.

Based strictly on user design requirements, external filtering of the current signal may be desired. The initial

location that can be considered for the filter is at the output of the current amplifier. Although placing the filter

at the output satisfies the filtering requirements, this location changes the low output impedance measured by

any circuitry connected to the output voltage pin. The other location for filter placement is at the current amplifier

input pins. This location also satisfies the filtering requirement, but carefully select the components to minimize

the impact on device performance. Figure 9-1 shows a filter placed at the inputs pins.

+

–

REF2

REF1

VS

GND

OUT

PWM

Rejection

IS+

IS–

IN+

IN–

SH+

SH–

400 µ

50 k

50 k

Figure 9-1. Filter at Input Pins

External series resistance provides a source of additional measurement error. Therefore, keep the value of these

series resistors to 10 Ω or less to reduce loss of accuracy. The internal bias network shown in Figure 9-1 creates

a mismatch in input bias currents when a differential voltage is applied between the input pins (see Figure 9-2).

If additional external series filter resistors are added to the circuit, a mismatch is created in the voltage drop

across the filter resistors. This voltage is a differential error voltage in the shunt resistor voltage. In addition to the

absolute resistor value, mismatch resulting from resistor tolerance can significantly impact the error because this

value is calculated based on the actual measured resistance.

www.ti.com

INA254

SLOS974 – JUNE 2021

Copyright © 2021 Texas Instruments Incorporated

Submit Document Feedback

13

Product Folder Links: INA254