[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)
2
tan (πfbn/fs)
1 − tan (πfbn/fs)
1 + tan (πfbn/fs)
An = kn x
,
Cn =
Bn = cos(2π fon/fs) x
,
1 + tan (πfbn/fs)
1 + tan (πfbn/fs)
(n = 2, 3, 4)
Transfer function
1 − z −2
1− Bnz −1− Cnz −2
(n = 2, 3, 4)
hn (z) = An
The center frequency should be set as below.
fon / fs < 0.497
MS1402-E-06
2013/02
- 81 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
