Datasheet

0
20
40
60
80
100
120
140
-
-
-
-
-
-
-
NormalizedFrequency(f /f )
IN MOD
Gain(dB)
0.010 0.070.02 0.03 0.04 0.05 0.06
DR[2:0]=000
DR[2:0]=110
0
20
40
60
80
100
120
140
-
-
-
-
-
-
-
Normalized Frequency (f /f )
IN MOD
Gain (dB)
0.05 0.10 0.50.15 0.2 0.25 0.3 0.35 0.4 0.45
DR[2:0] = 110
DR[2:0] = 000
0
-20
-40
-60
-80
-100
-120
-140
Normalized Frequency (f /f )
IN DR
Gain (dB)
1 20 3 4 50.5 4.53.52.51.5
0
0.5
1
1.5
2
2.5
3
-
-
-
-
-
-
Normalized Frequency (f /f )
IN DR
Gain (dB)
0.05 0.10 0.15 0.350.2 0.25 0.3
ADS131E04
ADS131E06
ADS131E08
www.ti.com SBAS561A –JUNE 2012–REVISED APRIL 2013
The sinc filter has notches (or zeroes) that occur at the output data rate and multiples thereof. At these
frequencies, the filter has infinite attenuation. Figure 23 shows the sinc filter frequency response and Figure 24
shows the sinc filter roll-off. With a step change at the input, the filter takes 3 t
DR
to settle. After a rising edge of
the START signal, the filter takes t
SETTLE
time to output settled data. The filter settling times at various data rates
are discussed in the START subsection of the SPI Interface section. Figure 25 and Figure 26 show the filter
transfer function until f
MOD
/ 2 and f
MOD
/ 16, respectively, at different data rates. Figure 27 shows the transfer
function extended until 4 f
MOD
. It can be seen that the ADS131E0x passband repeats itself at every f
MOD
. The
input R-C antialiasing filters in the system should be chosen such that any interference in frequencies around
multiples of f
MOD
are attenuated sufficiently.
Figure 23. Sinc Filter Frequency Response Figure 24. Sinc Filter Roll-Off
Figure 25. Transfer Function of On-Chip Figure 26. Transfer Function of On-Chip
Decimation Filters Until f
MOD
/ 2 Decimation Filters Until f
MOD
/ 16
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