The measurement error expected from the additional external filter resistors can be calculated using Equation 4,

and the gain error factor is calculated using Equation 5.

Gain Error (%) = 100

(100

Gain Error Factor)

-

´

(4)

The gain error factor, shown in Equation 4, can be calculated to determine the gain error introduced by the

additional external series resistance. Equation 4 calculates the deviation of the shunt voltage, resulting from the

attenuation and imbalance created by the added external filter resistance. Table 9-2 provides the gain error

factor and gain error for several resistor values.

Gain Error Factor =

(5)

Where:

• R1 is the INA281-Q1 input resistance value specified in Table 8-1.

Table 9-2. Example Gain Error Factor and Gain Error for 10-Ω External Filter Input Resistors

DEVICE (GAIN)

GAIN ERROR FACTOR

GAIN ERROR (%)

A1 devices (20)

0.99658

–0.34185

A2 devices (50)

0.99598

–0.40141

A3 devices (100)

0.99598

–0.40141

A4 devices (200)

0.99499

–0.50051

A5 devices (500)

0.99203

–0.79663

9.2 Typical Application

The INA281-Q1 is a unidirectional, current-sense amplifier capable of measuring currents through a resistive

shunt with shunt common-mode voltages from –4 V to +110 V.

GND

MCU

24 V

Solenoid

5 V

INA

R

SENSE

I

SENSE

ADC

Figure 9-2. Current Sensing in a Solenoid Application

9.2.1 Design Requirements

In this example application, the common-mode voltage ranges from 0 V to 24 V. The maximum sense current is

1.5 A, and a 5-V supply is available for the INA281-Q1. Following the design guidelines from Section 9.1.1, a R

design setup for this application.

INA281-Q1

SBOSA01 – NOVEMBER 2020

www.ti.com

16

Submit Document Feedback

Copyright © 2020 Texas Instruments Incorporated

Product Folder Links: INA281-Q1