AsahiKASEI AK4493, Manual

Page: 55 / 104

[AK4493]
017012230-E-00 2017/12
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Digital Filter
Six types of digital filter in PCM mode and two types of digital filter in DSD mode are available in the
AK4493 for sound color selection of music playback.
In PCM mode, the digital filter can be selected by the SD, SLOW and SSLOW pins if the AK4493 is in Pin
Control Mode, and it can be selected by the SD, SLOW and SSLOW bits in Register Control Mode (
Table
25 ).
Table 25. Digital Filter Setting
SSLOW SD SLOW Mode
0 0 0 Sharp Roll-off filter
0 0 1 Slow Roll-off filter
0 1 0 Short Delay Sharp Roll-off filter (default)
0 1 1 Short Delay Slow Roll-off filter
1 0 * Super Slow Roll-off filter
1 1 * Low Dispersion Short Delay filter
(*: Do not care)
In DSD mode, the cutoff frequency of digital filter can be switched by the DSDF bit. Table 26 shows the
cutoff frequency @fs = 44.1 kHz. The cutoff frequency tracks the sampling frequency (fs). Do not set
GC[2:0] bits to
“100” when DSDD bit = “0” and DSDF bit = “1”. Otherwise a pop noise may occur.
Table 26. DSD Filter Select
DSDF bit
Cut Off Frequency @fs=44.1kHz
DSD64 DSD128 DSD256 DSD512
0 39kHz 78kHz 156kHz 312kHz (default)
1 76kHz 152kHz 304kHz 608kHz
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De-emphasis Filter (PCM)
A digital de-emphasis filter is available for 32kHz*, 44.1kHz or 48kHz* sampling rates (tc = 50/15µs) and
is enabled or disabled by the DEM pin or DEM1-0 bits. DEM1-0 bits are ignored in DSD and EXDF
modes. DEM setting value is held even if the data mode is switched among PCM, DSD and EXDF modes.
*(32kHz and 48kHz de-emphasis are supported in Register Control Mode only.)
Table 27. De-emphasis Control (Register Control Mode)
DEM1 DEM0 Mode
0 0 44.1kHz
0 1 OFF (default)
1 0 48kHz
1 1 32kHz
Table 28. De-emphasis Control (Pin Control Mode)
DEM Pin Mode
L 44.1kHz
H OFF (default)