Cirrus Logic CS5571 - Manual (Page 22)

CS5571
22 DS768PP1
3/25/08
10:56
Figures 14 and 15 illustrate the small signal performance of the CS5571 with a 5.55 kHz signal at -80 dB
down. Figure 14 is with DITHER on and Figure 15 is with DITHER off. At -80 dB the signal is 1/10,000
of full scale, having a peak-to-peak magnitude of only a few codes. For small signals, DNL errors and
quantization errors can introduce distortion because the error in the code size, or the quantization error
without adequate dither, are a much greater percentage of the signal than with a full-scale input. Figure
15, with DITHER off, illustrates that distortion components can be introduced when there is not adequate
dither to randomize the quantization error.
Figures 16 and 17 illustrate DITHER on and DITHER off with a 5.55 kHz input at -100 dB. At -100 dB the
signal is only about 41 microvolts peak to peak. This is less than the one code width which is about
62.5 microvolts.
-160
-140
-120
-100
-80
-60
-40
-20
0
0 10k 20k 30k 40k 50k
Frequency (Hz)
-160
-140
-120
-100
-80
-60
-40
-20
0
0 10k 20k 30k 40k 50k
Frequency (Hz)
5.55 kHz, -80 dB
32k Samples @ 100 kSps
Dither On
Figure 14. Spectral Performance, -80 dB
Dither On
Figure 15. Spectral Performance, -80 dB
Dither Off
-160
-140
-120
-100
-80
-60
-40
-20
0
0 10k 20k 30k 40k 50k
Frequency (Hz)
-160
-140
-120
-100
-80
-60
-40
-20
0
0 10k 20k 30k 40k 50k
Frequency (Hz)
Figure 16. Spectral Performance, -100 dB
Dither On
Figure 17. Spectral Performance, -100 dB
Dither Off