AK4671_10 Datasheet, PDF (64/166 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/RCV/HP-AMP

[AK4671]
(3) Stereo Separation Emphasis Filter (FIL3)
FIL3 is used to emphasize the stereo separation of stereo mic recording data or playback data. F3A13-0 and F3B13-0 bits
set the filter coefficient of FIL3. FIL3 becomes High Pass Filter (HPF) at F3AS bit = “0”, and Low Pass Filter (LPF) at
F3AS bit = “1”. FIL3 bit controls ON/OFF of FIL3. When Stereo Separation Emphasis Filter is OFF, the audio data
passes this block by 0dB gain. The coefficient should be set when FIL3 bit = “0” or PMADL = PMADR = PMDAL =
PMDAR bits = “0”.
1) When FIL3 is set to “HPF”
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting (Note 61)
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB=F3A0, F3B0)
1 / tan (πfc/fs)
A = 10^K/20 x
,
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
2) When FIL3 is set to “LPF”
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting (Note 61)
FIL3: F3AS bit = “1”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB= F3A0, F3B0)
1
A = 10^K/20 x
,
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
MS0666-E-02
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2010/06