SBAS949A February 2020 – February 2021 ADS131M06
An analog low-pass filter is required in front of each of the channel inputs to prevent out-of-band noise and interferers from coupling into the band of interest. Because the ADS131M06 is a delta-sigma ADC, the integrated digital filter provides substantial attenuation for frequencies outside of the band of interest up to the frequencies adjacent to fMOD. Therefore, a single-order RC filter provides sufficient antialiasing protection in the vast majority of applications.
Choosing the values of the resistor and capacitor depends on the desired cutoff frequency, limiting source impedance for the ADC inputs, and providing enough instantaneous charge to the ADC input sampling circuit through the filter capacitor. Figure 9-1 shows the recommended filter component values. These recommendations are sufficient for CLKIN frequencies between 2 MHz and 8.2 MHz.