AK4955 Datasheet, PDF (53/117 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP/ LDO & DSP

[AK4955]
■ De-emphasis Filter
A digital de-emphasis filter is available for 32kHz, 44.1kHz or 48kHz sampling rates (tc = 50/15µs) by IIR filter and it is
controlled by DEM1-0 bits. These bits select the input frequency for the filtering. (Table 39)
DEM1 bit DEM0 bit
Mode
0
0
44.1kHz
0
1
OFF
(default)
1
0
48kHz
1
1
32kHz
Table 39. De-emphasis Filter Control
■ Output Digital Volume (Manual Mode)
The ALC block becomes output digital volume (manual mode) by setting ALC2 bit to “0” when PMPFIL = PMDAC bits
= “1” and ADCPF bit is “0”. The output digital volume gain is set by the OVL7-0 bit and the OVR7-0 bits (Table 40).
When the OVOLC bit = “1”, the OVL7-0 bits control both L and R channel volume levels. When the OVOLC bit = “0”,
the OVL7-0 bits control L channel volume level and the OVR7-0 bits control R channel volume level. When changing the
volumes, zero cross detection is executed on both L and R channels independently. The OVOL value is changed at zero
crossing or timeout. The zero crossing timeout period is set by ZTM1-0 bits.
OVL7-0 bits
OVR7-0 bits
GAIN [dB]
Step
F1H
+36.0
F0H
+35.625
EFH
+35.25
:
:
0.375dB
92H
+0.375
91H
0.0
90H
-0.375
:
:
2H
-53.625
1H
-54.0
0H
MUTE
Table 40. Output Digital Volume Setting
(default)
When writing to the OVL7-0 bits and OVR7-0 bits continuously, the control register should be written in an interval more
than zero crossing timeout. If not, the zero crossing counters are reset at each time and the volume will not be changed.
However, when writing the same register values as the previous time, the zero crossing counter will not be reset, so that it
could be written in an interval less than zero crossing timeout.
MS1343-E-00
- 53 -
2011/12