AK4753 Datasheet, PDF (40/85 Pages) Asahi Kasei Microsystems – 2-in, 4-out CODEC with DSP Functions

[AK4753]
■ Digital Volume and Gain Control
The AK4753 has three volume controls as gain setting of the amplifier outputs. Digital volume control is the general
volume to adjust the output signal level in normal operation. Pre-Gain and Post-Gain are for gain setting of the signal
level in the signal path.
1. Digital Volume (DATT)
The Ak4753 has a built-in channel independent digital volume (DATT) with 256 levels in 0.5dB steps including
MUTE. The transition time between the set levels by L7-0 bits (R7-0 bits) can be set by DVTM bit. When DVTM bit =
“0” (Table 25), the transition time from 0dB(00H) to MUTE(FFH) is 1024/fs (21.3ms@fs=48kHz). When the PDN pin
is set to “L”, the volume level is initialized to MUTE(FFH). The transition between the set levels is soft transition.
Therefore a switching noise does not occur within the transition. When the PMSAR bit = “1”, the volume and gain
follows the SAR value and the register setting of DATT (L/R7-0 bits) is invalid.
L/R7-0 bits
Attenuation Level
00H
0dB
01H
−0.5dB
02H
−1.0dB
03H
−1.5dB
:
:
FDH
−126.5dB
FEH
−127.0dB
FFH
MUTE (−∞)
(default)
Table 24. Digital Volume ATT Value
DVTM bit
ATT speed
0dB to MUTE
1 step
0
1024/fs
4/fs
(default)
1
256/fs
1/fs
Table 25. Transition Time among ATT7-0 Setting Values of the Digital Volume
2. Pre-Gain
The AK4753 has the four steps volume before a limiter circuit. The volume levels of L channel and R channel are
in common in one DSP block, but levels between two DSP blocks are independent. Volume levels are set by
1PREG1-0 and 2PREG1-0 bits (Table 26). When the set level is changed, a switching noise occurs because the
volume level is re-written by the register directory.
1PREG1-0 bits
2PREG1-0 bits
GAIN(dB) Step
00
0.0
(default)
01
+6.0
6.0dB
10
+12.0
11
+18.1
Table 26. Pre-Gain Setting
3. Post-Gain
The AK4753 has the four steps volume after the limiter circuit. The volume levels of L channel and R channel are
in common in one DSP block, but those levels between two DSP blocks are independent. Volume levels are set by
1PSTG1-0 and 2PSTG1-0 bits (Table 27). When the set level is changed, a switching noise occurs because the
volume level is re-written by the register directory.
1PSTG1-0 bits
2PSTG1-0 bits
GAIN(dB)
00
0.0
(default)
01
+3.5
10
+6.0
11
+8.0
Table 27. Post-Gain Setting
MS1311-E-00
- 40 -
2011/07