AK4649 Datasheet, PDF (54/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
■ Output Digital Volume 3
The AK4649 has a digital output volume control (256 levels, linear step, MUTE). It is processed before the DAC block.
The input data of DAC is changed from 0 to –48.13dB or MUTE. This volume has a soft transition function. Therefore no
switching noise occurs during the transition. Transition time from 0dB to MUTE is 255/fs, and each 1level transition
takes 1/fs. Volume calculating formula is shown in Table 45. This volume control is also available during ALC operation.
DVOL7-0 bits ATT_DATA GAIN(0dB)
FFH
FEH
FDH
:
255
+0
(default)
254
-0.034
253
-0.068
:
:
02H
2
-42.11
01H
1
-48.13
00H
-
Mute
Table 44. Output Digital Volume3 Setting
DVOL7-0 bits
GAIN (dB)
FFH
:
20 log₁₀ (ATT_DATA / 255)
01H
00H
Mute
Table 45. Output Digital Volume 3 Formula
■ Digital HPF1
A digital High Pass Filter (HPF) is integrated for DC offset cancellation of the ADC input. The cut-off frequencies of the
HPF1 are set by HPFC1-0 bits (Table 46). It is proportional to the sampling frequency (fs) and default is 3.4Hz (@fs =
44.1kHz). HPFAD bit controls the ON/OFF of the HPF1 (Recommend HPF enable).
HPFC1 bit
0
0
1
1
HPFC0 bit
0
1
0
1
fc
fs=44.1kHz
fs=22.05kHz
3.4Hz
1.7Hz
13.6Hz
6.8Hz
108.8Hz
54.4Hz
217.6Hz
108.8Hz
Table 46. HPF1 Cut-off Frequency
fs=8kHz
0.62Hz
2.47Hz
19.7Hz
39.5Hz
(default)
MS1023-E-01
- 54 -
2010/08