AK4679EG Datasheet, PDF (81/220 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with DSP and MIC/RCV/HP/SPK/LINE-AMP

[AK4679]
2. EQ2, EQ3, EQ4: Equalizer
5E2A15-0, 5E2B15-0 and 5E2C15-0 bits set the coefficient of EQ2. 5E3A15-0, 5E3B15-0 and 5E3C15-0 bits set the
coefficient of EQ3. 5E4A15-0, 5E4B15-0 and 5E4C15-0 bits set the coefficient of EQ4.
fs: Sampling frequency
fo₂ ~ fo₄: Center frequency
fb₂ ~ fb₄: Band width where the gain is 3dB different from center frequency
k₂ ~ k₄: Filter gain
Register setting (Note 78)
EQ2: 5E2A[15:0] bits =A₁, 5E2B[15:0] bits =B₁, 5E2C[15:0] bits =C₂
EQ3: 5E3A[15:0] bits =A₂, 5E3B[15:0] bits =B₂, 5E3C[15:0] bits =C₃
EQ4: 5E4A[15:0] bits =A₃, 5E4B[15:0] bits =B₃, 5E4C[15:0] bits =C₄
(MSB=5E2A15, 5E2B15, 5E2C15, 5E3A15, 5E3B15, 5E3C15, 5E4A15, 5E4B15, 5E4C15; LSB= 5E2A0,
5E2B0, 5E2C0, 5E3A0, 5E3B0, 5E3C0, 5E4A0, 5E4B0, 5E4C0)
A_n = k_n x
tan (πfb_n/fs)
1 + tan (πfb_n/fs)
(n = 2, 3, 4)
, B_n = cos(2π fo_n/fs) x
2
1 + tan (πfb_n/fs)
, ^{Cn =}
1 − tan (πfb_n/fs)
1 + tan (πfb_n/fs)
Transfer function
h_n (z) = A_n
1 − z ^−2
1− B_nz ^−1− C_nz ^−2
(n = 2, 3, 4)
The center frequency should be set as below.
fo_n / fs < 0.497
MS1402-E-06
- 81 -
2013/02