[AK4492]
■ De-emphasis Filter (PCM Mode)
A digital de•emphasis filter is available for 32kHz, 44.1kHz or 48kHz sampling rates (tc = 50/15µs) and is
enabled or disabled by DEM1-0 pins or DEM1-0 bits. When DSD mode or EXDF mode, DEM1-0 bits are
ignored. The setting value is held even if PCM, DSD and EXDF mode is switched.
Table 30. De-emphasis Control
DEM1
DEM0
Mode
44.1 kHz
OFF
48 kHz
32 kHz
0
0
1
1
0
1
0
1
(default)
■ Output Volume (PCM Mode, DSD Mode, EXDF Mode)
The AK4492 includes channel independent digital output volumes (ATTL/R) with 256 levels at 0.5dB step
including MUTE. When changing output levels, it is executed in soft transition thus no switching noise
occurs during these transitions. It can attenuate the input data from 0dB to -127dB and mute when
assuming the output signal level is 0dB when ATTL/R[7:0] bits = “FFH”.
Table 31. Attenuation level of Digital Attenuator
ATTL/R[7:0]bits
Attenuation Level
(register 03-04H)
FFH
FEH
FDH
:
+0 dB
-0.5 dB
-1.0 dB
:
(default)
02H
01H
00H
-126.5 dB
-127.0 dB
MUTE (-∞)
The transition time of digital output volume is set by ATS[1:0] bits (Table 32). When changing output
levels between Mode0-3, it is executed in soft transition thus no switching noise occurs during these
transitions. Register setting values will be kept even switching the PCM and DSD modes.
Table 32. Transition Time between Set Values of ATT[7:0] bits
Mode ATS1 ATS0
ATT speed
EXDF bit = “0”,
DP bit = “0”
4080/fs
EXDF bit = “1”
DP bit = “0”
4080*WCK Cycle
2040*WCK Cycle
510*WCK Cycle
255*WCK Cycle
DP bit = “1”
0
1
2
3
0
0
1
1
0
1
0
1
4080/(2*fs)
2040/(2*fs)
510/(2*fs)
255/(2*fs)
(default)
2040/fs
510/fs
255/fs
It takes 4080/fs (92.5ms@fs=44.1kHz) from “FFH” (0dB) to “00H” (MUTE) in Mode 0. The attenuation
level is initialized to “FFH” (0dB) by setting the PDN pin = “L”.
If the volume is changed during reset period, the output volume will become a setting value after releasing
the reset. It will change to a setting value immediately if the volume is changed within 5/fs after releasing
reset.
016011073-E-00
2016/12
- 62 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
