Cirrus Logic CS5376A - Manual (Page 49)

CS5376A
DS612F4 49
FIR1 – Single stage, fixed decimate by 4
Coefficient set 0: linear phase decimate by 4, 48 coefficients
Coefficient set 1: minimum phase decimate by 4, 48 coefficients
SINC droop compensation filter
FIR2 – Single stage, fixed decimate by 2
Coefficient set 0: linear phase decimate by 2, 126 coefficients
Coefficient set 1: minimum phase decimate by 2, 126 coefficients
Brick wall low-pass filter, flat to 40% f
s
Combined SINC + FIR digital filter specifications
Passband ripple less than +/- 0.01 dB below 40% f
s
Transition band -3 dB frequency at 42.89% f
s
Stopband attenuation greater than 130 dB above 50% f
s
Figure 26. FIR Filter Stages
SINC + FIR filters
FIR2
Output
Word
Rate SINC
Deci-
mation FIR1
Deci-
mation FIR2
Deci-
mation Total
Deci-
mation Passband
Ripple
( ± dB)
Stopband
Atten-
uation
(dB)
4000 16 4 2 128 0.0042 130.38
2000 32 4 2 256 0.0045 130.38
1000 64 4 2 512 0.0040 130.42
500 128 4 2 1024 0.0041 130.42
333 192 4 2 1536 0.0080 130.45
250 256 4 2 2048 0.0064 130.43
200 320 4 2 2560 0.0041 130.43
125 512 4 2 4096 0.0046 130.42
100 640 4 2 5120 0.0040 130.43
50 1280 4 2 10240 0.0040 130.43
40 1600 4 2 12800 0.0036 130.43
25 2560 4 2 20480 0.0040 132.98
20 3200 4 2 25600 0.0036 130.43
10 6400 4 2 51200 0.0036 130.43
5 12800 4 2 102400 0.0036 130.43
1 64000 4 2 512000 0.0029 134.31
Table 12. FIR Filter Characteristics