TI recommends placing an RC filter in front of the isolated amplifier 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 (20 MHz) of the ΔΣ modulator
• The input bias current does not generate significant voltage drop across the DC impedance of the input filter
• The impedances measured from the analog inputs are equal

For most applications the structure shown in Figure 8-2 achieves excellent performance.

Figure 8-2 Differential Input Filter