ADS131B04-Q1
ZHCSMK3B –NOVEMBER 2020 –REVISED NOVEMBER 2021
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samples available from the ADS131B04-Q1 after a supply ramp or reset have the noise performance and
frequency response corresponding to the fast-settling filter as specified in the Electrical Characteristics table,
whereas subsequent samples have the noise performance and frequency response consistent with the sinc3
filter. See the Fast Start-Up Behavior section for more details regarding the fast start-up capabilities of the
ADS131B04-Q1.
8.3.8.1.2 SINC3 and SINC3 + SINC1 Filter
The ADS131B04-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 and calibration logic. For OSR
settings of 2048 and higher, the sinc3 filter is followed by a sinc1 filter. As shown in 表 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 ADS131B04-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. 表8-5 lists the settling times
of the sinc3 and sinc3 + sinc1 filters for each OSR setting. The ADS131B04-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 表 8-5 has expired can be considered fully
settled.
表8-5. Digital Filter Settling Times
OSR (Overall)
128
OSR (SINC3)
OSR (SINC1)
SETTLING TIME (tMOD)
128
N/A
N/A
N/A
N/A
2
432
816
256
256
512
512
1584
3120
6192
10288
18480
34864
1024
1024
2048
1024
4096
1024
4
8192
1024
8
16384
1024
16
8.3.8.2 Digital Filter Characteristic
方程式 4 calculates the z-domain transfer function of a sinc3 filter that is used for OSRs ranging from 128 to
1024:
3
1 - Z -N
H z
( )
=
N 1 - Z -1
(4)
where:
• N is the OSR
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