Estimating differential error

AN4304

14/20

DocID024731 Rev 1

A similar bode diagram to Figure 12: "Bode diagram" is obtained with the following poles:

From Equation 5 we can extrapolate that at frequencies much higher than ω2, the

differential voltage error, due to the mismatch of the Ccm1 and Ccm2 capacitances, is

given by Equation 6 below:

We can now re-estimate the differential error (Vdiff) as follows:

Vin = triangular AC at 100 kHz, 5 Vpp

Rs = 10 Ω

Ccm = 2.2 µF with a tolerance of 20 %

Ccm1 = 2.2 µF +20 % = 2.64 µF

Ccm2 = 2.2 µF -20 % = 1.76 µF

So, Vdiff = 52 mVpp.