AK4497 Datasheet, PDF (57/98 Pages) Asahi Kasei Microsystems – Quality Oriented 32-Bit 2ch DAC

[AK4497]
■ Digital Filter
Six types of digital filter in PCM mode and two types of digital filter in DSD mode are available in the
AK4497 for sound color selection of music playback.
In PCM mode, digital filter can be selected by the SD, SLOW and SSLOW pins if the AK4497 is in pin
control mode, and digital filter can be selected by SD, SLOW and SSLOW bits in register control mode
(Table 27).
In register control mode, programmable digital filter can be available by setting SSLOW bit = “1” and SD
bit = “1”. In this case, Low dispersion short delay filter is available if SLOW bit = “0” and the coefficient
can be changed if SLOW bit = “1”.
Table 27. 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
0
Super Slow roll Off filter
1
0
1
Super Slow roll Off filter
1
1
X
Low dispersion Shot delay filter /
Programmable FIR filter
(Note 41)
Note 41. SSLOW=1, SD=1, SLOW=0: Low dispersion Short delay filter
SSLOW=1, SD=1, SLOW=1: Programmable FIR filter (only for register control mode)
In DSD mode, the cutoff frequency of digital filter can be switched by DSDF bit. Table 28 shows the cutoff
frequency of fs = 44.1kHz. The cutoff frequency tracks the sampling frequency (fs). Do not set GS[2:0]
bits to “100” when DSDD bit = “0” and DSDF bit = “1”. Otherwise a pop noise may occur.
DSDF bit
0
1
Table 28. DSD Filter Select
Cut Off Frequency @fs=44.1kHz
DSD64fs DSD128fs DSD256fs DSD512fs
39kHz
76kHz
78kHz
152kHz
156kHz
304kHz
312kHz (default)
608kHz
Rev. 0.1
- 57 -
2015/11