SBASAD2 November 2021 ADS130B04-Q1
The ADS130B04-Q1 selects the sinc3 filter path two conversions after power-up or device reset. For OSR settings of 128 to 1024, the sinc3 filter output directly feeds into the global-chop logic. For OSR settings of 2048 and higher, the sinc3 filter is followed by a sinc1 filter. As shown in Table 8-5, the sinc3 filter operates at a fixed OSR of 1024 in this case while the sinc1 filter implements the additional OSRs of 2 to 16. That means, when an OSR of 4096 (for example) is selected, the sinc3 filter operates at an OSR of 1024 and the sinc1 filter at an OSR of 4.
The filter has infinite attenuation at integer multiples of the data rate except for integer multiples of fMOD. Like all digital filters, the digital filter response of the ADS130B04-Q1 repeats at integer multiples of the modulator frequency, fMOD. The data rate and filter notch frequencies scale with fMOD.
When possible, plan frequencies for unrelated periodic processes in the application for integer multiples of the data rate such that any parasitic effect they have on data acquisition is effectively canceled by the notches of the digital filter. Avoid frequencies near integer multiples of fMOD whenever possible because tones in these bands can alias to the band of interest.
The sinc3 and sinc3 + sinc1 filters for a given channel require time to settle after a channel is enabled, the channel multiplexer or gain setting is changed, or a resynchronization event occurs. Table 8-5 lists the settling times of the sinc3 and sinc3 + sinc1 filters for each OSR setting. The ADS130B04-Q1 does not gate unsettled data. Therefore, the host must account for the filter settling time and disregard unsettled data if any are read. The data at the next DRDY falling edge after the filter settling time listed in Table 8-5 has expired can be considered fully settled.
|OSR (Overall)||OSR (SINC3)||OSR (SINC1)||SETTLING TIME (tMOD)|