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

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-20

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0

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50k

Frequency (Hz)

-160

-140

-120

-100

-80

-60

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-20

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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

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30k

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Frequency (Hz)

-160

-140

-120

-100

-80

-60

-40

-20

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30k

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Frequency (Hz)

Figure 16. Spectral Performance, -100 dB

Dither On

Figure 17. Spectral Performance, -100 dB

Dither Off