AK4679EG Datasheet, PDF (84/220 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with DSP and MIC/RCV/HP/SPK/LINE-AMP

[AK4679]
■ Dynamic Range Control
DRC Block
PMDRC
DATT-A
SMUTE
Mono/
Stereo
DRCM1-0
LPF
HPF
Noise
Suppression
NSLPF
NSLA13-0
NSLB13-0
NSHPF
NSHA13-0
NSHB13-0
NSCE
NSTHL4-0
NSTHH4-0
NSREF3-0
NSATT2-0
NSGAIN2-0
NSIAFS1-0
NSOAFS1-0
LPF
DLLPF1-0
DLLA13-0
DLLB13-0
HPF
DMHPF1-0
DMHA13-0
DMHB13-0
LPF
DMLPF1-0
DMLA13-0
DMLB13-0
HPF
DHHPF1-0
DHHA13-0
DHHB13-0
VOLL
VL1X/Y5-0
VL2X/Y5-0
VL3X/Y4-0
L1G6-0
L2G6-0
L3G6-0
L4G6-0
VOLM
VM1X/Y5-0
VM2X/Y5-0
VM3X/Y4-0
M1G6-0
M2G6-0
M3G6-0
M4G6-0
VOLH
DVLCL
DVLCM
DVLCH
VH1X/Y5-0
VH2X/Y5-0
VH3X/Y4-0
H1G6-0
H2G6-0
H3G6-0
H4G6-0
DAF1-0
DVLMAT2-0
DVRGAIN2-0
VOL
DRC
Limiter
DAC
DRCC1-0 DLMAT1-0
DRGAIN1-0
Figure 68. DRC Functions and Signal Path
DRCM1-0 bits select stereo or mono of DRC input data. In case of mono mode, the same data is input to both channels.
DRCM1 bit DRCM0 bit
Lch
Rch
0
0
L
R
(default)
0
1
L
L
1
0
R
R
1
1
N/A
Table 41. DRC Stereo/Mono Select (N/A: Not available)
1. Noise Suppression Block
(1) Low Pass Filter (LPF)
This is composed with 1st order LPF. NSLA13-0 bits and NSLB13-0 bits set the coefficient of LPF. NSLPF 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 NSLPF bit = “0” or PMDRC bit = “0”. The LPF starts operation 4/fs(max) after when NSLPF bit = “1” and
PMDRC bit = “1” are set.
fs: Sampling frequency
fc: Cut-off frequency
Register setting
LPF: NSLA[13:0] bits =A, NSLB[13:0] bits =B
(MSB=NSLA13, NSLB13; LSB=NSLA0, NSLB0)
1
A=
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 + z ^−1
H(z) = A
1 + Bz ^−1
The cut-off frequency should be set as below.
fc/fs ≥ 0.05 (fc min = 2205Hz at 44.1kHz)
MS1402-E-06
- 84 -
2013/02