AK4679EG Datasheet, PDF (95/220 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with DSP and MIC/RCV/HP/SPK/LINE-AMP

[AK4679]
(3) High Frequency Range
HPF
VOLH
DVLCH
“0” data
(DHHPF1-0 bits = “00”)
DHHPF1-0
DHHA13-0
DHHB13-0
VH1X/Y5-0
VH2X/Y5-0
VH3X/Y4-0
H1G6-0
H2G6-0
H3G6-0
H4G6-0
Figure 73. DVLC Functions and Signal Path for High Frequency Range
(3-1) High Pass Filter (HPF)
This is composed with 1st or 2nd order HPF. The coefficient of HPF is set by DHHA13-0 bits and DHHB13-0 bits. HPF
bit controls ON/OFF of the HPF. When the HPF is OFF, the audio data does not pass this block. The coefficient must be
set when DHHPF1-0 bits = “00” or PMDRC bit = “0”. The HPF starts operation 4/fs(max) after when DHHPF1-0 bits =
“01” or “10” and PMDRC bit = “1” are set.
DHHPF1 bit DHHPF0 bit
Mode
0
0
OFF (“0” data) (default)
0
1
1st order HPF
1
0
2nd order HPF
1
1
N/A
Table 58. DHHPF Mode Setting (N/A: Not available)
fs: Sampling frequency
fc: Cut-off frequency
Register setting
HPF: DHHA[13:0] bits =A, DHHB[13:0] bits =B
(MSB=DHHA13, DMHB13; LSB=DHHA0, DHHB0)
1 / tan (πfc/fs)
A=
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function (1st order)
1 − z ^−1
H(z) = A
1 + Bz ^−1
Transfer function (2nd order)
1 − z ^−1
1 − z ^−1
H(z) = A
xA
1 + Bz ^−1
1 + Bz ^−1
The cut-off frequency should be set as below.
fc/fs ≥ 0.0001 (fc min = 4.41Hz at 44.1kHz)
MS1402-E-06
- 95 -
2013/02