JAJSHV4C January 2014 – August 2019 ADS1283
PRODUCTION DATA.
The high-performance modulator is an inherently-stable, fourth-order, ΔΣ, 2 + 2 pipelined structure, as Figure 30 shows. The modulator shifts the quantization noise to a higher frequency (out of the pass band), where the noise can be easily removed by digital filtering. The modulator data can either be completely filtered by the on-chip digital filter or partially filtered by the onboard sinc filter in conjunction with external, post-processing filters.
The modulator performance is optimized for input signals over the dc to 2-kHz bandwidth. As Figure 31 shows, the effect of PGA and modulator chop result in spectral artifacts at the chop frequency (4 kHz) and related odd-order harmonics to the chop frequency. When using the sinc filter mode in conjunction with an external post-decimation filter, design the external digital filter to suppress the modulator chopping artifacts.