8.2.3 Input Filter Design

TI recommends placing an RC filter in front of a ΔΣ modulator to improve signal-to-noise performance of the signal path. Design the input filter such that:

• The cutoff frequency of the filter is at least one order of magnitude lower than the sampling frequency of the ΔΣ modulator
• The DC impedance of the filter does not generate significant voltage drop in the analog input lines
• The source impedance of the analog inputs are equal

For most applications, the structure shown in Figure 52 achieves excellent performance.

Figure 52. Differential Input Filter