GND

MCU

24 V

Solenoid

5 V

INA

R

SENSE

I

SENSE

ADC

Gain Error Factor =

16

INA281

SBOSA29 – JUNE 2020

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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 4 provides the gain error factor

and gain error for several resistor values.

Where:

•

•

R1 is the INA281 input resistance value specified in Table 1.

•

(5)

Table 4. 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

8.2 Typical Application

The INA281 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.

Figure 30. Current Sensing in a Solenoid Application

8.2.1 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. Following the design guidelines from RSENSE and Device

Table 5 lists the design setup for this application.

Table 5. Design Parameters

DESIGN PARAMETERS

EXAMPLE VALUE

Power supply voltage

5 V

Common mode voltage range

0 V to 24 V

Maximum sense current

1.5 A

50 mΩ

Gain option

50 V/V