+

±

REF2

REF1

VS

GND

OUT

IN+

IN±

PWM

Rejection

50 k

50 k

10

INA240-Q1

SBOS808A – AUGUST 2016 – REVISED DECEMBER 2016

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Copyright © 2016, Texas Instruments Incorporated

9 Detailed Description

9.1 Overview

The INA240-Q1 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.

9.2 Functional Block Diagram

9.3 Feature Description

9.3.1 Amplifier Input Signal

The INA240-Q1 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.

9.3.1.1 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-Q1 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-Q1 to provide minimal output transients and

ringing compared with standard circuit approaches.

9.3.1.2 Input Signal Bandwidth

The INA240-Q1 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-Q1 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.