AK4695 Datasheet, PDF (37/107 Pages) Asahi Kasei Microsystems – 24bit 4ch CODEC with MIC/HP/SPK/LINE-AMP

[AK4695]
A_n = K_n x
(n = 1, 2)
tan (fb_n/fs)
1 + tan (fb_n/fs)
2
, B_n = cos(2 fo_n/fs) x
, ^{Cn =}
1 + tan (fb_n/fs)
1  tan (fb_n/fs)
1 + tan (fb_n/fs)
Transfer function
H(z) = 1 + h₁(z) + h₂(z)
h_n (z) = A_n
1  z ^2
1 B_nz ^1 C_nz ^2
(n = 1, 2)
The center frequency must be set as below.
0.003 < fo_n / fs < 0.497
When gain of K is set to “-1”, this equalizer becomes a notch filter. When EQ1 EQ2 is used as a notch filter, central
frequency of a real notch filter deviates from the above-mentioned calculation, if its central frequency of each band is near.
The control software that is attached to the evaluation board has functions that revises a gap of frequency and calculates the
coefficient. When its central frequency of each band is near, the central frequency should be revised and confirm the
frequency response.
Note 49. [[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 2¹³
X must be rounded to integer, and then should be translated to binary code (2’s complement).
MSB of each filter coefficient setting register is sign bit.
The power consumption can be reduced by setting HPF1, HPF2, LPF, EQ1 or EQ2 off while either PMPFIL2 or PMPFIL3
bit is “0”, or either PMPFIL0 or PMPFIL1bit is “0”.
MS1463-E-01
- 37 -
2014/12