Cirrus-logic AN299 Manual de usuario descargar pdf (Pagina 7)

AN299REV1 7

AN299

magnitude resulting in higher weights for the new reading. See Figure 5 to compare the step responses of these

algorithms.

Figure 5. Algorithm Step Response Comparison

Figures 5a, 5b, 5c, and 5d illustrate the typical peak-to-peak noise performance of a CS5532AS with a gain of 64

and word rate of 60 Sps. Figure 5a shows the noise performance without software filtering and the other three plots

illustrate the effects of applying different software filtering algorithms. Without any software filtering, the peak-to-

peak noise is 64 codes or 6 bits, which is consistent with the data sheet’s specification of 18 noise-free bits. With

the simple running average of 8 algorithm, approximately one more bit of noise-free performance can be gained

(peak-to-peak noise of 35 codes), while the simple exponential average of 8 gives slightly better improvement (27

codes peak-to-peak). The simple exponential average of 64 results in approximately 8 codes peak-to-peak or a

noise-free resolution improvement of 3 bits.

Averaging Algorithm Responses

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

18000000

-10 0 10 20 30 40 50 60 70 80 90 100

Number of conversions

Output Code

Exponential Avg. of 8

Running Avg. of 8

Adaptive Avg. of 8

Exp Avg. of 64

1 2 3 4 5 6 7 8 9 10

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Cirrus-logic AN299 Manual de usuario Pagina 7