[AK4425A]
■ Output Volume
The AK4425A includes channel independent digital output volumes (ATT) with 256 levels at linear step including
MUTE. These volumes are in front of the DAC and can attenuate the input data from 0dB to –48dB and mute. When
changing levels, transitions are executed via soft changes; thus no switching noise occurs during these transitions. The
transition time of 1 level and all 256 levels is shown in Table 8.
Transition Time
Sampling Speed
1 Level
4LRCK
8LRCK
255 to 0
Normal Speed Mode
Double Speed Mode
Quad Speed Mode
1020LRCK
2040LRCK
4080LRCK
16LRCK
Table 8. ATT Transition Time
■ Soft Mute Operation
Soft mute operation is performed in digital domain. When the SMUTE bit is set to “1”, the output signal is attenuated by
-∞ during ATT_DATA×ATT transition time (Table 8) from the current ATT level. When the SMUTE bit is returned to
“0”, the mute is cancelled and the output attenuation gradually changes to the ATT level during ATT_DATA×ATT
transition time. If the soft mute is cancelled before attenuating to -∞, the attenuation is discontinued and returned to ATT
level by the same cycle. The soft mute is effective for changing the signal source without stopping the signal transmission.
SMUTE bit
(1)
(1)
ATT Level
Attenuation
(3)
-∞
GD
GD
(2)
AOUT
Notes:
(1) ATT_DATA×ATT transition time (Table 8). For example, in Normal Speed Mode, this time is 1020LRCK cycles
(1020/fs) at ATT_DATA=255.
(2) The analog output corresponding to the digital input has group delay, GD.
(3) If the soft mute is cancelled before attenuating to -∞ after starting the operation, the attenuation is discontinued and
returned to ATT level by the same cycle.
Figure 11. Soft Mute function
MS1127-E-01
2011/03
- 16 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
