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 internal 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

Most voltage sensing applications use high-impedance resistor dividers in front of the isolated amplifier to scale down the input voltage. In this case, a single capacitor as given in Figure 7-2 is sufficient to filter the input signal.

Figure 7-2 Differential Input Filter