AK4373 Datasheet, PDF (47/98 Pages) Asahi Kasei Microsystems – Low Power Stereo DAC with HP/SPK-Amp

[AK4373]
(4) EQ
fs: Sampling frequency
fc₁: Pole frequency
fc₂: Zero-point frequency
f: Input signal frequency
K: Filter gain [dB] (Maximum +12dB)
Register setting (Note 41)
EQA[15:0] bits =A, EQB[13:0] bits =B, EQC[15:0] bits =C
(MSB=EQA15, EQB13, EQC15; LSB=EQA0, EQB0, EQC0)
1 + 1 / tan (πfc₂/fs)
A = 10^K/20 x
,
1 + 1 / tan (πfc₁/fs)
1 − 1 / tan (πfc₁/fs)
B=
,
1 + 1 / tan (πfc₁/fs)
1 − 1 / tan (πfc₂/fs)
C =10^K/20 x
1 + 1 / tan (πfc₁/fs)
Transfer function
H(z) =
A + Cz ^−1
1 + Bz ^−1
M(f) =
Amplitude
A² + C² + 2ACcos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
(AB−C)sin (2πf/fs)
θ(f) = tan ^−1
A + BC + (AB+C)cos (2πf/fs)
Note 41. [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 should 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.
MS0991-E-00
- 47 -
2008/09