ak4141 AKM Semiconductor, Inc., ak4141 Datasheet - Page 23

• Manufacturer Part Number: ak4141
• Description: Nicam/a2/eia-j Digital Stereo Decoder
• Manufacturer: AKM Semiconductor, Inc.

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(1) Stereo Separation Emphasis Filter (FIL3)
FIL3 is used to emphasize the stereo separation of stereo data. F3A1[13:0], F3A2[13:0] and F3B1[13:0], F3B1[13:0] bits
set the filter coefficient of FIL3 for SDTO1/2 respectively. FIL3 becomes High Pass Filter (HPF) at F3AS1/2 bit = “1”,
and Low Pass Filter (LPF) at F3AS1/2 bit = “0”. F3BP1/2 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 F3BP1/2 bit =
“0”.
1) When FIL3 is set to “HPF”
2) When FIL3 is set to “LPF”
MS0952-E-00
Digital Programmable Filter Circuit
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting
FIL3: F3AS1/2 bit = “1”, F3A1[13:0], F3A1[13:0] bits =A, F3B1[13:0], F3B2[13:0] bits =B
(MSB=F3A113(F3A213), F3B13(F3B213); LSB=F3A10(F3A20), F3B10(F3B20))
Transfer function
FIL3: F3AS1/2 bit = “0”, F3A1[13:0], F3A1[13:0] bits =A, F3B1[13:0], F3B2[13:0] bits =B
(MSB= F3A113(F3A213), F3B13(F3B213); LSB= F3A10(F3A20), F3B10(F3B20))
Transfer function
A = 10
H(z) = A
A = 10
H(z) = A
K/20
K/20
x
x
1 + Bz
1 + Bz
(Figure
(Figure
1 − z
1 + z
1 + 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
1 / tan (πfc/fs)
−1
−1
−1
−1
15)
15)
1
,
,
B =
B =
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
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[AK4141]
2008/05