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AK4679EG Datasheet, PDF (70/220 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with DSP and MIC/RCV/HP/SPK/LINE-AMP | |||
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[AK4679]
(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 = â0â, and Low Pass Filter (LPF) at
F3AS bit = â1â. 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 = â0â or PMPFIL bit = â0â. The FIL3 starts
operation 4/fs(max) after when FIL3 bit = â1â and PMPFIL bit = â1â are set.
1) When FIL3 is set to âHPFâ
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ⥠K ⥠â10dB)
Register setting (Note 77)
FIL3: F3AS bit = â0â, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB=F3A0, F3B0)
1 / tan (Ïfc/fs)
A = 10K/20 x
,
1 + 1 / tan (Ïfc/fs)
1 â 1 / tan (Ïfc/fs)
B=
1 + 1 / tan (Ïfc/fs)
Transfer function
1 â z â1
H(z) = A
1 + Bz â1
2) When FIL3 is set to âLPFâ
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ⥠K ⥠â10dB)
Register setting (Note 77)
FIL3: F3AS bit = â1â, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB= F3A0, F3B0)
1
A = 10K/20 x
,
1 + 1 / tan (Ïfc/fs)
1 â 1 / tan (Ïfc/fs)
B=
1 + 1 / tan (Ïfc/fs)
Transfer function
1 + z â1
H(z) = A
1 + Bz â1
MS1402-E-06
- 70 -
2013/02
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