Texas Instruments ADS1274, Manual

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0
- 1
-
2
-
3
-
4
-
5
-
6
-
7
- 8
- 9
- 10
Normalized Input Frequency (f /f
IN T DA A
)
Amplitude(dB)
0.45 0.47 0.49 0.51 0.53 0.55
0
- 20
- 40
- 60
- 80
- 100
- 120
- 140
0.50
Normalized Input Frequency (f
IN
/f
DATA
)
Amplitude(dB)
0 0.25 0.75 1
20
0
-
20
-
40
-
60
-
80
-
100
-
120
-
140
-
160
Gain(dB)
Normalized Input Frequency (f /f
IN DATA
)
0 32 64 96 128
0.02
0
-
0.02
- 0.04
-
0.06
- 0.08
-
0.10
0.2
Normalized Input Frequency (f /f
IN DATA
)
Amplitude(dB)
0 0.1 0.3 0.4 0.5 0.6
ADS1274
ADS1278
www.ti.com SBAS367F – JUNE 2007 – REVISED FEBRUARY 2011
High-Resolution Mode
The oversampling ratio is 128 in High-Resolution
mode.
Figure 62 shows the frequency response in
High-Resolution mode normalized to f
DATA
. Figure 63
shows the passband ripple, and the transition from
passband to stop band is shown in
Figure 64 . The
overall frequency response repeats at multiples of the
modulator frequency f
MOD
(128 × f
DATA
), as shown in
Figure 65 . The stop band of the ADS1274/78
provides 100dB attenuation of frequencies that begin
just beyond the passband and continue out to f
MOD
.
Placing an antialiasing, low-pass filter in front of the
ADS1274/78 inputs is recommended to limit possible
high-amplitude out-of-band signals and noise. Often,
a simple RC filter is sufficient.
Table 4 lists the image
rejection versus external filter order.
Figure 64. Transition Band Response for
High-Resolution mode
Figure 62. Frequency Response for
High-Resolution Mode
Figure 65. Frequency Response Out to f
MOD
for
High-Resolution Mode
Figure 63. Passband Response for
High-Resolution Mode
© 2007 – 2011, Texas Instruments Incorporated
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