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

where the gain error factor is calculated using Equation 5.

Gain Error (%) = 100 x (Gain Error Factor í 1)

(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 8-2 provides the gain error

factor and gain error for several resistor values.

Gain Error Factor =

(5)

Where:

• R1 is the INAx290 input resistance value specified in Table 7-1.

Table 8-2. 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

8.2 Typical Application

The INAx290 is a unidirectional, current-sense amplifier capable of measuring currents through a resistive shunt

with shunt common-mode voltages from 2.7 V to 120 V. The circuit configuration for monitoring current in a high-

side radio frequency (RF) power amplifier (PA) application is shown in Figure 8-2.

54 V

RF

Out

RF

DAC

GND

ADC

Microprocessor

INAx290

GND

Figure 8-2. Current Sensing in a PA Application

8.2.1 Design Requirements

application.

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INA290, INA2290

SBOS961B – JUNE 2020 – REVISED DECEMBER 2020

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