AK4373 Datasheet, PDF (45/98 Pages) Asahi Kasei Microsystems – Low Power Stereo DAC with HP/SPK-Amp

[AK4373]
[Filter Coefficient Setting]
(1) High Pass Filter (HPF)
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
Register setting (Note 41)
HPF: F1A[13:0] bits =A, F1B[13:0] bits =B
(MSB=F1A13, F1B13; LSB=F1A0, F1B0)
1 / tan (πfc/fs)
A=
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 − z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
Amplitude
2 − 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
(2) Low Pass Filter (LPF)
fs: Sampling frequency
fc: Cut-off frequency
f: Input signal frequency
Register setting (Note 41)
LPF: F2A[13:0] bits =A, F2B[13:0] bits =B
(MSB=F2A13, F2B13; LSB=F2A0, F2B0)
1
A=
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 + z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
Amplitude
2 + 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
(B+1)sin (2πf/fs)
θ(f) = tan ^−1
1 - B + (B−1)cos (2πf/fs)
Phase
θ(f) = tan ^−1
(B−1)sin (2πf/fs)
1 + B + (B+1)cos (2πf/fs)
MS0991-E-00
- 45 -
2008/09