AK4950 Datasheet, PDF (47/106 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP & mini DSP

[AK4950]
2) When EQ1 ~ EQ4 = Dip boost Filter
fs: Sampling Frequency
fo: Center Furequency
α = sin (2πfc/fs) / 2Q
A = Boost gain Example) Boost gain = +12dB (A = 10 ^{Gain [dB] / 40}) when A=2.
Q = fo/BW (BW: Band Width)
A (1+ αA)
A0 = _{A + α}
–2Acos (2πfc/fs)
A1 =
A+α
A (1– αA)
A2 = _{A + α}
2Acos (2πfc/fs)
B1 =
A+α
A– α
B2 = _{A + α}
The cut-off frequency must be set as below.
EQ1, EQ4: 0.0625 < fo_n / fs < 0.497
EQ2, EQ3: fo_n / fs < 0.497
Setting Example) EQ2 (Notch Filter ) fs = 44.1kHz, fo = 8kHz, BW =200Hz (I₂C mode)
A0 = 0FD201 (hex): Addr. A0H
A1 = F2C80F (hex): Addr. A1H
A2 = 0FD201 (hex): Addr. A2H
B1 = 0D37F1 (hex): Addr. A3H, A5H
B2 = F05BFE (hex): Addr. A4H, A6H
Note 37.
[Translation the filter coefficient calculated by the equations above from real number to binary code (2’s complement)]
X = (Real number of filter coefficient calculated by the equations above) x 2²⁰
X should be rounded to integer, and then should be translated to binary code (2’s complement).
MSB of each filter coefficient setting register is sine bit.
MS1320-E-00
- 47 -
2011/10