Cirrus-logic CS5571 Manual de usuario descargar pdf (Pagina 23)

CS5571

DS768PP1 23

3/25/08

10:56

Figure 18 illustrates a test signal of 5.55 kHz, 116.3 dB down, which is only 6.3 microvolts peak to peak,

or about 1/10 of a code width. The converter can reliably digitize this signal because of its excellent DNL

and proper dither.

Figure 19 is a spectral plot of the converter with its input grounded. The spectral information is on a log-

arithmic frequency axis as this illustrates the very low frequency behavior of the converter. Figure 19 was

produced from averaging the results of 16 FFT outputs using 2 million samples each. This plot also illus-

trates that the converter noise floor is free of spurious components that may be present in other converters

due to on-chip digital interference.

-160

-140

-120

-100

-80

-60

-40

-20

0 10k 20k 30k 40k 50

Frequency (Hz)

Figure 18. Spectral Performance, -116.3 dB

Dither On

-140

-120

-100

-80

0.1 1 10 100 1k 10k

-160

-180

-60

-40

-20

Frequency (Hz)

Shorted Input

2M Samples @ 100 kSps

16 Averages

Figure 19. Spectral Plot of Noise with Shorted Input

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 33 34

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Cirrus-logic CS5571 Manual de usuario Pagina 23