Datasheet

[AK4646]
MS0557-E-06 2011/06
- 35 -
(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 = PMDAC 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 36)
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB=F3A0, F3B0)
A = 10
K/20
x
1 / tan (
π
fc/fs)
1 + 1 / tan (
π
fc/fs)
B =
1
−
1 / tan (
π
fc/fs)
1 + 1 / tan (
π
fc/fs)
,
Transfer function
H(z) = A
1
−
z
−
1
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 36)
FIL3: F3AS bit = “1”, F3A [13:0] bits =A, F3B [13:0] bits =B
(MSB=F3A13, F3B13; LSB= F3A0, F3B0)
A = 10
K/20
x
1
1 + 1 / tan (
π
fc/fs)
B =
1
−
1 / tan (
π
fc/fs)
1 + 1 / tan (
π
fc/fs)
,
Transfer function
H(z) = A
1 + z
−
1
1 + Bz
−
1