ZHCS146C December 2011 – April 2020 ADS1291 , ADS1292 , ADS1292R
PRODUCTION DATA.
Each channel of the ADS1291, ADS1292, and ADS1292R has a 24-bit ΔΣ ADC. This converter uses a second-order modulator optimized for low-power applications. The modulator samples the input signal at the rate of fMOD = fCLK / 4 or fCLK / 16, as determined by the CLK_DIV bit. In both cases, the sampling clock has a typical value of 128 kHz. As in the case of any ΔΣ modulator, the ADS1291, ADS1292, and ADS1292R noise is shaped until fMOD / 2, as shown in Figure 24. The on-chip digital decimation filters explained in the Digital Decimation Filter section can be used to filter out the noise at higher frequencies. These on-chip decimation filters also provide antialias filtering. This feature of the ΔΣ converters drastically reduces the complexity of analog antialiasing filters that are typically needed with nyquist ADCs.
Figure 24. Power Spectral Density (PSD) of a ΔΣ Modulator (4-Bit Quantizer)