CS5571 View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS5571' PDF : 32 Pages View PDF
3/25/08
10:56
CS5571
Figure 20 illustrates a noise histogram of 4096 samples with the input signal adjusted to almost the exact
center of a code with DITHER on. Figure 21 illustrates a noise histogram of 4096 samples with the input
signal at the center of a code with DITHER off.
Notice that with a signal at the center of a code that the converter outputs the same code over 96% of the
time. Figures 22 and 23 illustrate the noise histogram, DITHER on and then DITHER off with the input
signal at a code boundary. Notice that in the DITHER off case the converter only exhibits two codes of
noise.
4500
4000
3500
3000
2500
2624
2000
1500
1000
709
751
500
3
9
0
-2
-1
0
1
2
Output (Codes)
Figure 20. Noise Histogram, 4096 Samples
Dither On, Code Center
4500
4000
3940
3500
3000
2500
2000
1500
1000
500
0
75
81
0
0
-2
-1
0
1
2
Output (Codes)
Figure 21. Noise Histogram, 4096 Samples
Dither Off, Code Center
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0
-2
1953
2019
58
66
-1
0
1
2
Output (Codes)
Figure 22. Noise Histogram, 4096 Samples
Dither On, Input at Code Boundary
4500
4000
3500
3000
2500
2000
2050 2046
1500
1000
500
0
0
0
0
-2
-1
0
1
2
Output (Codes)
Figure 23. Noise Histogram, 4096 Samples
Dither Off, Input at Code Boundary
3.9 DITHER
From the performance plots, one should conclude that the best AC performance for small signals occurs
with DITHER on. For capturing multiple samples and performing averaging, DITHER should also be on
because the dither will randomize the quantization noise of the converter and provide improved accuracy.
However, if only one conversion is to be taken on a DC input, DITHER should be set to off. With DITHER
off, the converter exhibits only two codes of noise if the signal is at any point other than the exact center
of a code. This means that with DITHER off the converter will nominally yield over 32,000 noise-free
counts.
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DS768PP1
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