• GAIN is the gain of the current-sense amplifier.

Table 8-1 shows an example of the different results obtained from using five different gain versions of the

INA290-Q1. From the table data, the highest gain device allows a smaller current-shunt resistor and decreased

power dissipation in the element.

PARAMETER(1)

EQUATION

INA290A1Q

INA290A2Q

INA290A3Q

INA290A4Q

INA290A5Q

G

Gain

20 V/V

50 V/V

100 V/V

200 V/V

500 V/V

Ideal differential input voltage (Ignores

swing limitation and power supply

variation.)

250 mV

100 mV

50 mV

25 mV

10 mV

Current sense resistor value

25 mΩ

10 mΩ

5 mΩ

2.5 mΩ

1 mΩ

Current-sense resistor power dissipation

2.5 W

1 W

0.5W

0.25 W

0.1 W

(1)

Design example with 10-A full-scale current with maximum output voltage set to 5 V.

8.1.2 Input Filtering

Note

Input filters are not required for accurate measurements using the INA290-Q1, and use of filters in this

location is not recommended. If filter components are used on the input of the amplifier, follow the

guidelines in this section to minimize the effects on performance.

Based strictly on user design requirements, external filtering of the current signal may be desired. The initial

location that can be considered for the filter is at the output of the current-sense amplifier. Although placing the

filter at the output satisfies the filtering requirements, this location changes the low output impedance measured

by any circuitry connected to the output voltage pin. The other location for filter placement is at the current-sense

amplifier input pins. This location also satisfies the filtering requirement, but the components must be carefully

selected to minimally impact device performance. Figure 8-1 shows a filter placed at the input pins.

IN+

IN±

OUT

V

CM

-

+

Buffer

Current

Feedback

V

S

GND

RL

R1

R1

Bias

Load

R

SENSE

I

SENSE

R

IN

R

IN

C

IN

f

1

Figure 8-1. Filter at Input Pins

External series resistance provides a source of additional measurement error, so keep the value of these series

resistors to 10 Ω or less to reduce loss of accuracy. The internal bias network shown in Figure 8-1 creates a

mismatch in input bias currents (see Figure 6-15, Figure 6-16, and Figure 6-17) when a differential voltage is

applied between the input pins. If additional external series filter resistors are added to the circuit, a mismatch is

created in the voltage drop across the filter resistors. This voltage is a differential error voltage in the shunt

resistor voltage. In addition to the absolute resistor value, mismatch resulting from resistor tolerance can

significantly impact the error because this value is calculated based on the actual measured resistance.

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INA290-Q1

SBOS995A – OCTOBER 2019 – REVISED NOVEMBER 2020

Copyright © 2020 Texas Instruments Incorporated

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Product Folder Links: INA290-Q1