[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 = “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 PMPFIL bit = “0”. The FIL3 starts
operation 4/fs(max) after when FIL3 bit = “1” and PMPFIL bit = “1” are set.
1) When FIL3 is set to “HPF”
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting (Note 77)
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB=F3A0, F3B0)
1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
A = 10K/20
x
,
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 77)
FIL3: F3AS bit = “1”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB= F3A0, F3B0)
1
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
A = 10K/20
x
,
B =
1 + 1 / tan (πfc/fs)
Transfer function
1 + z −
1
H(z) = A
1 + Bz −
1
MS1402-E-06
2013/02
- 70 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
