8.3 Feature Description

8.3.1 Adjustable Gain Setting

pins (pins 2 and 3).

+

±

+

±

+

±

5 k

3 k

5 k

5 k

5 k

3 k

RG

REF

+VS

OUT

+V

S

íVS

íIN

+IN

O

IN

IN

REF

V

G V

V

V

RG

R

G

100 nF

100 nF

Figure 8-1. Simplified Diagram of the INA849 with Output Equation

G = 1+

6 NŸ

R

G

(1)

Table 8-1 lists several commonly used gains and resistor values. The 6-kΩ term in Equation 1 is a result of the

sum of the two internal 3-kΩ feedback resistors. These on-chip resistors are laser-trimmed to accurate, absolute

values. The accuracy and temperature coefficients of these resistors are included in the gain accuracy and drift

specifications of the INA849.

Table 8-1. Commonly Used Gains and Resistor Values

DESIRED GAIN (V/V)

CALCULATED GAIN

(V/V)

CALCULATED GAIN

ERROR (%)

1

Not connected

N/A

N/A

2

6.04 k

1.9933

0.33

5

1.50 k

5

0

10

665

10.022

–0.23

20

316

19.987

0.06

50

121

50.586

–1.17

100

60.4

100.337

–0.34

200

30.1

200.335

–0.17

500

12.1

496.867

0.63

1000

6.04

994.377

0.56

The 5-kΩ feedback resistors in the output stage are ratiometrically matched to achieve unity-gain stability. These

resistors may shift up to 15% depending on production.

As shown in Figure 8-1 and explained in more detail in Figure 11-1, make sure to connect low-ESR, 0.1-µF,

ceramic bypass capacitors between each supply pin and ground, placed as close to the device as possible.

www.ti.com

INA849

SBOS945B – NOVEMBER 2020 – REVISED APRIL 2021

Copyright © 2021 Texas Instruments Incorporated

Submit Document Feedback

17

Product Folder Links: INA849