Input signals occurring near f_MOD (12.8 MHz in high-speed mode and 1.6 MHz in low-speed mode) fold back (or alias) to the pass band, resulting in data errors. When aliased, the frequency errors cannot be removed by post processing. An analog antialias filter at the ADC inputs removes the frequencies from the input signal before they are aliased by the ADC. The required order of the antialias filter is dependent on the selected OSR and the target value of signal attenuation at f_MOD. A large value of OSR means more frequency range between the f_DATA Nyquist frequency and f_MOD for the filter to provide the desired roll off. For example, for OSR = 128, more than two decades of frequency separates f_DATA and f_MOD. With a corner frequency = f_DATA, a third-order, 60-dB per decade filter provides a 120-dB alias rejection at f_MOD.