6 Detailed Description

6.1 Overview

The INA281-Q1 is a high- or low-side current-sense amplifier that offers a wide common-mode range, precision

zero-drift topology, excellent common-mode rejection ratio (CMRR), high bandwidth, and fast slew rate. Different

gain versions are available to optimize the output dynamic range based on the application. The INA281-Q1 is

designed using a transconductance architecture with a current-feedback amplifier that enables low bias currents

of 20 µA with a common-mode voltage of 110 V.

6.2 Functional Block Diagram

IN+

IN±

OUT

-

+

Buffer

Current

Feedback

VS

GND

RL

R1

R1

Bias

Load

RSENSE

ISENSE

Load

Supply

6.3 Feature Description

6.3.1 Amplifier Input Common-Mode Signal

The INA281-Q1 supports large input common-mode voltages from –4 V to +110 V. Because of the internal

topology, the common-mode range is not restricted by the power-supply voltage (VS). This allows for the

INA281-Q1 to be used for both low- and high-side current-sensing applications.

6.3.1.1 Input-Signal Bandwidth

The INA281-Q1 –3-dB bandwidth is gain-dependent, with several gain options of 20 V/V, 50 V/V, 100 V/V, 200

V/V, and 500 V/V. The unique multistage design enables the amplifier to achieve high bandwidth at all gains.

This high bandwidth provides the throughput and fast response that is required for the rapid detection and

processing of overcurrent events.

The bandwidth of the device also depends on the applied VSENSE voltage. Figure 6-1 shows the bandwidth

performance profile of the device over frequency as output voltage increases for each gain variation. As shown

in Figure 6-1, the device exhibits the highest bandwidth with higher VSENSE voltages, and the bandwidth is

higher with lower device gain options. Individual requirements determine the acceptable limits of error for

high-frequency, current-sensing applications. Testing and evaluation in the end application or circuit is required

to determine the acceptance criteria and validate whether or not the performance levels meet the system

specifications.

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INA281

SBOSA29A – JUNE 2020 – REVISED NOVEMBER 2023

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