AK4951AEN Datasheet, PDF (44/105 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/HP/SPK-AMP

[AK4951A]
■ Digital Programmable Filter Circuit
(1) High Pass Filter (HPF2)
This is composed 1st order HPF. The coefficient of HPF is set by F1A13-0 bits and F1B13-0 bits. HPF bit
controls ON/OFF of the HPF2. When the HPF2 is OFF, the audio data passes this block by 0dB gain. The
coefficient must be set when PMPFIL bit = “0” or HPF bit = “0”. The HPF2 starts operation 4/fs (max) after
when HPF bit = PMPFIL bit = “1” is set.
fs: Sampling Frequency
fc: Cutoff Frequency
Register Setting (Note 37)
HPF: F1A[13:0] bits =A, F1B[13:0] bits =B
(MSB=F1A13, F1B13; LSB=F1A0, F1B0)
1 / tan (fc/fs)
1  1 / tan (fc/fs)
A=
, B=
1 + 1 / tan (fc/fs)
1 + 1 / tan (fc/fs)
Transfer Function
1  z ^1
H(z) = A
1 + Bz ^1
The cut-off frequency must be set as below.
fc/fs  0.0001 (fc min = 4.8Hz at 48kHz)
(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 must be set when PMPFIL bit = “0” or LPF bit = “0”. The LPF starts operation 4/fs (max) after
when LPF bit =PMPFIL bit= “1” is set.
fs: Sampling Frequency
fc: Cutoff Frequency
Register Setting (Note 37)
LPF: F2A[13:0] bits =A, F2B[13:0] bits =B
(MSB=F2A13, F2B13; LSB=F2A0, F2B0)
1
1  1 / tan (fc/fs)
A=
, B=
1 + 1 / tan (fc/fs)
1 + 1 / tan (fc/fs)
Transfer Function
1 + z ^1
H(z) = A
1 + Bz ^1
The cut-off frequency must be set as below.
fc/fs  0.05 (fc min = 2400Hz at 48kHz)
016001936-E-00
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2016/03