AK7755EN_16 Datasheet, PDF (90/109 Pages) Asahi Kasei Microsystems – DSP with Mono ADC Stereo CODEC + Mic/Lineout Amp

[AK7755]
■ DAC Blocks
1. De-emphasis Filter
The AK7755 has a digital de-emphasis filter (tc=50/15µs) by IIR filter, corresponding to 48kHz
sampling frequency. DEM[1:0] bits control the de-emphasis filter.
DEM mode
0
1
2
3
DEM[1:0] Sampling Frequency (fs)
00
OFF
01
48kHz
10
44.1kHz
11
32kHz
Table 7. De-emphasis Control
(default)
2. DAC Digital Volume Control
The DACs of the AK7755 have channel independent volume control (256 levels, 0.5 step). The
VOLDAL/R[7:0] bits (CONT18: D7-D0 / CONT19: D7-D0), set the attenuation level of each DAC
channel.
DAC Lch VOLDAL
[7:0]
DAC Rch VOLDAR [7:0] Attenuation Level
00h
00h
+12.0dB
01h
01h
+11.5dB
02h
02h
+11.0dB
:
:
:
17h
17h
+0.5dB
18h
18h
0.0dB
19h
19h
-0.5dB
:
:
:
FDh
FDh
-114.5dB
FEh
FEh
-115.0dB
FFh
FFh
Mute (-∞)
Table 8. DAC Digital Volume Setting
(default)
Transition time between set values can be selected by ATSPDA bit (CONT0C: D5).
MODE
ATSPDA
ATT speed
0
0
1/fs
1
1
4/fs
Table 9. DAC Volume Transition Time Setting
The transition between set values is soft transition of 1021 levels in Mode 0. It takes 1021/fs
(21.3ms@fs=48kHz) from 00h to FFh (MUTE) in Mode 0. If the PDN pin is set to “L”, the
VOLDAL/R[7:0] bits are initialized to 18h.
014006643-E-00
- 90 -
2014/10