8 Detailed Description

8.1 Overview

The INA240 is a current-sense amplifier that offers a wide common-mode range, precision, zero-drift topology,

excellent common-mode rejection ratio (CMRR), and features enhanced pulse width modulation (PWM)

rejection. Enhanced PWM rejection reduces the effect of common-mode transients on the output signal that

are associated with PWM signals. Multiple gain versions are available to allow for the optimization of the desired

full-scale output voltage based on the target current range expected in the application.

8.2 Functional Block Diagram

+

±

REF2

REF1

VS

GND

OUT

IN+

IN±

PWM

Rejection

50 k

50 k

8.3 Feature Description

8.3.1 Amplifier Input Signal

The INA240 is designed to handle large common-mode transients over a wide voltage range. Input signals from

current measurement applications for linear and PWM applications can be connected to the amplifier to provide

a highly accurate output, with minimal common-mode transient artifacts.

8.3.1.1 Enhanced PWM Rejection Operation

The enhanced PWM rejection feature of the INA240 provides increased attenuation of large common-mode

ΔV/Δt transients. Large ΔV/Δt common-mode transients associated with PWM signals are employed in

applications such as motor or solenoid drive and switching power supplies. Traditionally, large ΔV/Δt common-

mode transitions are handled strictly by increasing the amplifier signal bandwidth, which can increase chip size,

complexity and ultimately cost. The INA240 is designed with high common-mode rejection techniques to reduce

large ΔV/Δt transients before the system is disturbed as a result of these large signals. The high AC CMRR, in

conjunction with signal bandwidth, allows the INA240 to provide minimal output transients and ringing compared

with standard circuit approaches.

8.3.1.2 Input Signal Bandwidth

The INA240 input signal, which represents the current being measured, is accurately measured with minimal

disturbance from large ΔV/Δt common-mode transients as previously described. For PWM signals typically

associated with motors, solenoids, and other switching applications, the current being monitored varies at a

significantly slower rate than the faster PWM frequency.

The INA240 bandwidth is defined by the –3-dB bandwidth of the current-sense amplifier inside the device; see

the Electrical Characteristics table. The device bandwidth provides fast throughput and fast response required

for the rapid detection and processing of overcurrent events. Without the higher bandwidth, protection circuitry

may not have adequate response time and damage may occur to the monitored application or circuit.

INA240

SBOS662C – JULY 2016 – REVISED DECEMBER 2021

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