INA139

f

–3dB =

1

2 R

p

LCL

V

O

f

–3dB

R

L

C

L

3

4

Copyright © 2017, Texas Instruments Incorporated

Time

with buffer

without Buffer

14

INA139, INA169

SBOS181F – DECEMBER 2000 – REVISED FEBRUARY 2017

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Product Folder Links: INA139 INA169

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Copyright © 2000–2017, Texas Instruments Incorporated

Typical Applications (continued)

8.2.1.3 Application Curve

Figure 11. Driving an ADC With and Without a Buffer

8.2.2 Output Filter

Figure 12. Output Filter

8.2.2.1 Design Requirements

Filter the output of the INA139 or INA169 devices.

8.2.2.2 Detailed Design Procedure

A low-pass filter can be formed at the output of the INA139 or INA169 devices simply by placing a capacitor of

the desired value in parallel with the load resistor. First, determine the value of the load resistor required to

achieve the desired gain. See the table in Figure 9. Next, determine the capacitor value that results in the

desired cutoff frequency according to the equation shown in Figure 12. Figure 13 illustrates various combinations

of gain settings (determined by RL) and filter capacitors.