AN4304

Common mode filtering

DocID024731 Rev 1

9/20

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Common mode filtering

Figure 9: "Common mode filter at 7 kHz" shows a common mode filter with a cut-off

frequency at 7 kHz. The cut-off frequency is given by Equation 2:

It is recommended to place the same low path filter on each input of the current sensing to

equilibrate the two inputs. This avoids adding offset error. Note that particular care must be

taken in the choice of the resistances and the capacitances.

Figure 9: Common mode filter at 7 kHz