Cirrus Logic CS5509 - Manual (Page 14)

CS5509
14 DS125F3
line frequency interference will occur with the
CS5509 running at 32.768kHz.
Table 2. Filter Notch Attenuation (XIN = 32.768 kHz)
Anti-Alias Considerations for Spectral
Measurement Applications
Input frequencies greater than one half the output
word rate (CONV = 1) may be aliased by the con-
verter. To prevent this, input signals should be lim-
ited in frequency to no greater than one half the
output word rate of the converter (when CONV
=1). Frequencies close to the modulator sample rate
(XIN/2) and multiples thereof may also be aliased.
If the signal source includes spectral components
above one half the output word rate (when CONV
= 1) these components should be removed by
means of low-pass filtering prior to the A/D input
0
0 40
402.83
80
805.66
120
1208.5
160
1611.3
200
2014.2
240
2416.9
Frequency (Hz)
-160
-140
-120
-100
-80
-60
-40
-20
0
At
te
n
u
a
ti
o
n
(
d
B
)
XIN = 32.768 kHz
X1
X2
X1 = 32.768kHz
X2 = 330.00kHz
Figure 6. Filter Magnitude Plot to 260 Hz
0 5 10 15 20 25 30 35 40 45 50
Frequency (Hz)
-140
-120
-100
-80
-60
-40
-20
0
A
tt
e
nuat
ion
(
d
B
)
Flatness
dB
-0.010
-0.041
-0.093
-0.166
-0.259
-0.510
-0.667
-0.846
-1.047
-3.093
1
2
3
4
5
6
7
8
9
10
17
XIN = 32.768 kHz
Frequency
-0.374
Figure 7. Filter Magnitude Plot to 50 Hz
Frequency
(Hz)
Notch
Depth
(dB)
Frequency
(Hz)
Minimum
Attenuation
(dB)
50 125.6 50 ±1% 55.5
60 126.7 60 ±1% 58.4
100 145.7 100 ±1% 62.2
120 136.0 120 ±1% 68.4
150 118.4 150 ±1% 74.9
180 132.9 180 ±1% 87.9
200 102.5 200 ±1% 94.0
240 108.4 240 ±1% 104.4
0 5 10 15 20 25 30 35 40 45 50
Frequency (Hz)
-180
-135
-90
-45
0
45
90
135
180
Pha
s
e
(D
egre
es
)
XIN = 32.768 kHz
Figure 8. Filter Phase Plot to 50 Hz