= 10 kW

= 100 kW

= 1 kW

p

INA139-Q1

V

IN+

V

IN–

GND

V

O

R

L

C

L

R

L

C

L

OUT

13

INA139-Q1, INA169-Q1

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SGLS185F – SEPTEMBER 2003 – REVISED MAY 2016

Product Folder Links: INA139-Q1 INA169-Q1

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8.2.2 Output Filter

Filter the output of the INA139-Q1 or INA169-Q1 devices.

Figure 12. Output Filter

8.2.2.1 Design Requirements

For this design example, use the input parameters shown in Table 3.

Table 3. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Supply voltage, V+

INA139-Q1: 0 V to 40 V

INA169-Q1: 0 V to 60 V

Common-mode voltage, VCM

INA139-Q1: 0 V to 40 V

INA169-Q1: 0 V to 60 V

Full-scale shunt voltage, VSENSE

50 mV to 100 mV

Load resistor, RL

1 k

Ω to 100 kΩ

8.2.2.2 Detailed Design Procedure

A low-pass filter can be formed at the output of the INA1x9-Q1 simply by placing a capacitor of the desired value

in parallel with the load resistor. First, determine the value of the load resistor needed to achieve the desired gain

by using Table 1. Next, determine the capacitor value that results in the desired cutoff frequency according to the

equation shown in Figure 12. Figure 13 shows the frequency response with different RL values and a fixed filter

capacitor.

8.2.2.3 Application Curve

Figure 13. Gain vs Frequency