AK4695 Datasheet, PDF (51/107 Pages) Asahi Kasei Microsystems – 24bit 4ch CODEC with MIC/HP/SPK/LINE-AMP

[AK4695]
2. Dynamic Volume Control Block
The AK4695 has the dynamic volume control (DVLC) circuits before DRC. DVLC divides frequency range into three
band (Low, Middle and High) and controls independently. To set characteristics of the DVLC circuit around flat, it is
recommended that the cutoff frequencies of the LPF for Low Frequency Rage is set to the same value of cutoff frequency
of HPF for Middle Frequency Range, and the cutoff frequency of LPF for Middle Frequency Range is set to the same value
of cutoff frequency of HPF for High Frequency Range when using first order LPF and HFP. When using second order
filters, the cutoff frequency of the LPF for Low Frequency Range should be set to the value which is four times than the
HPF for Middle Frequency Range, and the cutoff frequency of the LPF for Middle Frequency Range should be set to the
value which is four times than the HPF for High Frequency Range.
(1) Low Frequency Range
LPF
VOLL
DVLCL
“0” data
(DLLPF1-0 bits = “00”)
DLLPF1-0
DLLA13-0
DLLB13-0
VL1X/Y5-0
VL2X/Y5-0
VL3X/Y4-0
L1G6-0
L2G6-0
L3G6-0
L4G6-0
Figure 34. DVLC Functions and Signal Path for Low Frequency Range
(1-1) Low Pass Filter (LPF)
This is composed with 1st or 2nd order LPF. DLLA13-0 bits and DLLB13-0 bits set the coefficient of LPF. DLLPF1-0 bits
controls ON/OFF of the LPF. When the LPF is OFF, the audio data does not pass this block. The coefficient must be set
when DLLPF1-0 bits = “00” or PMDRC bit = “0”. The LPF starts operation 4/fs(max) after when DLLPF1-0 bits = “01”
or “10” and PMDRC bit = “1” are set.
DLLPF1 bit DLLPF0 bit
Mode
0
0
OFF (“0” data)
(default)
0
1
1st order LPF
1
0
2nd order LPF
1
1
N/A
Table 47. DLLPF Mode Setting (N/A: Not Available)
fs: Sampling frequency
fc: Cut-off frequency
Register setting
LPF: DLLA[13:0] bits =A, DLLB[13:0] bits =B
(MSB=DLLA13, DLLB13; LSB=DLLA0, DLLB0)
1
A=
,
1 + 1 / tan (fc/fs)
1  1 / tan (fc/fs)
B=
1 + 1 / tan (fc/fs)
Transfer function (1st order)
1 + z ^1
H(z) = A
1 + Bz ^1
MS1463-E-01
- 51 -
2014/12