AN4304

Estimating differential error

DocID024731 Rev 1

13/20

The ripple is 111 mVpp which means that, in the worst case scenario, Vsense could be

equal to 205 mV instead of the expected value of 150 mV. This corresponds to an error of

37 %. To compensate the mismatching of the capacitances it is necessary to add one

differential capacitance, as shown in Figure 14: "Common and differential mode filter".

Figure 14: Common and differential mode filter

Equation 5 below expresses the transfer function of the common mode and differential

mode filtering. To simplify the calculation, only the mismatch of the capacitance is taken

into account. Vin is the voltage source.