CS5505(2009) Ver la hoja de datos (PDF) - Cirrus Logic

Número de pieza

componentes Descripción

Lista de partido

CS5505
(Rev.:2009)

Very Low Power, 16-Bit & 20-Bit A/D Converters

Cirrus Logic 

CS5505/6/7/8

CS5505/6/7/8

Digital Filter Characteristics

The digital filter in the CS5505/6/7/8 is the com-

bination of a comb filter and a low pass filter.

The comb filter has zeros in its transfer function

which are optimally placed to reject line interfer-

ence frequencies (50 and 60 Hz and their

multiples) when the CS5505/6/7/8 is clocked at

32.768 kHz. Figures 9, 10 and 11 illustrate the

magnitude and phase characteristics of the filter.

0

-20

X1 = 32.768kHz

X2 = 163.00kHz

-40

-60

-80

-100

-120

-140

-160

X1 0

X2 0

XIN = 32.768 kHz

40 80 120 160 200 240

198.97 397.95 596.92 795.10 993.87 1193.85

Frequency (Hz)

Figure 9. Filter Magnitude Plot to 260 Hz

0

-20

-40

-60

-80

-100

-120

Flatness

Frequency dB

1

-0.010

2

-0.041

3

-0.093

4

-0.166

5

-0.259

6

-0.374

7

-0.510

8

-0.667

9

-0.846

10 -1.047

17 -3.093

XIN = 32.768 kHz

-140

0

5 10 15 20 25 30 35 40 45 50

Frequency (Hz)

Figure 10. Filter Magnitude Plot to 50 Hz

Figure 9 illustrates the filter attenuation from dc

to 260 Hz. At exactly 50, 60, 100, and 120 Hz

the filter provides over 120 dB of rejection. Ta-

ble 3 indicates the filter attenuation for each of

the potential line interference frequencies when

the converter is operating with a 32.768 kHz

clock. The converter yields excellent attenuation

of these interference frequencies even if the fun-

damental line frequency should vary ±1% from

its specified frequency. The -3 dB corner fre-

quency of the filter when operating from a

32.768 kHz clock is 17 Hz. Figure 11 illustrates

that the phase characteristics of the filter are pre-

cisely linear phase.

Frequency

(Hz)

50

60

100

120

150

180

200

240

Notch

Depth

(dB)

125.6

126.7

145.7

136.0

118.4

132.9

102.5

108.4

Frequency Minimum

(Hz) Attenuation

(dB)

50±1%

55.5

60±1%

58.4

100±1%

62.2

120±1%

68.4

150±1%

74.9

180±1%

87.9

200±1%

94.0

240±1%

104.4

Table 3. Filter Notch Attenuation (XIN = 32.768 kHz)

180

135

90

45

0

-45

-90

-135

XIN = 32.768 kHz

-180

0

5 10 15 20 25 30 35 40 45 50

Frequency (Hz)

Figure 11. Filter Phase Plot to 50 Hz

DS59F74

19

Share Link: