ak4646 AKM Semiconductor, Inc., ak4646 Datasheet - Page 34

• Manufacturer Part Number: ak4646
• Description: Stereo Codec With Mic/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

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(1) High Pass Filter (HPF)
Normally, this HPF is used for a Wind-Noise Reduction Filter. This is composed with 2 steps of 1st order HPF. The
coefficient of both HPF is the same and set by F1A13-0 bits and F1B13-0 bits. HPFAD bit controls ON/OFF of the 1st
step HPF and HPF bit controls ON/OFF of the 2nd step HPF. When the HPF is OFF, the audio data passes this block by
0dB gain. The coefficient should be set when HPFAD=HPF bits = “0” or PMADL=PMADR= PMDAC bits = “0”.
Register setting (Note 34)
(2) Low Pass Filter (LPF)
This is composed with 1st order LPF. F2A13-0 bits and F2B13-0 bits set the coefficient of LPF. LPF bit controls ON/OFF
of the LPF. When the LPF is OFF, the audio data passes this block by 0dB gain. The coefficient should be set when LPF
bit = “0” or PMADL=PMADR=PMDAL=PMDAR bits = “0”.
Register setting (Note 34)
MS0557-E-02
Digital Programmable Filter Circuit
fs: Sampling frequency
fc: Cut-off frequency
fs: Sampling frequency
fc: Cut-off frequency
The cut-off frequency should be set as below.
The cut-off frequency should be set as below.
HPF: F1A[13:0] bits =A, F1B[13:0] bits =B
(MSB=F1A13, F1B13; LSB=F1A0, F1B0)
A =
Transfer function
LPF: F2A[13:0] bits =A, F2B[13:0] bits =B
(MSB=F2A13, F1B13; LSB=F2A0, F2B0)
A =
Transfer function
fc/fs ≥ 0.0001 (fc min = 4.41Hz at 44.1kHz)
fc/fs ≥ 0.05 (fc min = 2205Hz at 44.1kHz)
H(z) = A
H(z) = A
1 + 1 / tan (πfc/fs)
1 + 1 / tan (πfc/fs)
1 / tan (πfc/fs)
1 + Bz
1 + Bz
1 − z
1 + z
1
−1
−1
−1
−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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[AK4646]
2007/05