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[AK4675]
MS0963-E-00
2008/05
- 58 -
ミ
EXT Master Mode (PMPLL bit = “0”, M/S bit = “1”)
The AK4675 becomes EXT Master Mode by setting PMPLL bit = “0” and M/S bit = “1”. Master clock is input from the
MCKI pin, the internal PLL circuit is not operated. The clock required to operate is MCKI (256fs, 384fs, 512fs, 768fs or
1024fs). The input frequency of MCKI is selected by FS2-0 bits (
).
Mode
FS3 bit
FS2 bit
FS1 bit
FS0 bit
MCKI Input
Frequency
Sampling Frequency
Range
0
x
0 0 0 256fs 8kHz
∼
48kHz
1
x
0 0 1 1024fs 8kHz
∼
13kHz
4
x
1 0 0 384fs 8kHz
∼
48kHz
5
x
1 0 1 768fs 8kHz
∼
26kHz
6
x
1 1 0 512fs 8kHz
∼
26kHz
7
x
1 1 1 256fs 8kHz
∼
48kHz
(default)
Others Others
N/A
N/A
(N/A: Not available, x: Don’t care)
Table 13. MCKI Frequency at EXT Master Mode (PMPLL bit = “0”, M/S bit = “1”)
The S/N of the DAC at low sampling frequencies is worse than at high sampling frequencies due to out-of-band noise.
The out-of-band noise can be improved by using higher frequency of the master clock. The S/N of the DAC output
through the LOUT/ROUT pins at fs=8kHz is shown in
MCKI
S/N
(fs=8kHz, 20 A-weighted)
256fs 83dB
512fs 93dB
1024fs 93dB
Table 14. Relationship between MCKI and S/N of LOUT1/ROUT1 pins
MCKI should always be present whenever the ADC or DAC is in operation (PMADL bit = “1”, PMADR bit = “1”,
PMDAL bit = “0” or PMDAR bit = “1”). If MCKI is not provided, the AK4675 may draw excess current and it is not
possible to operate properly because utilizes dynamic refreshed logic internally. If MCKI is not present, the ADC and
DAC should be in the power-down mode (PMADL=PMADR=PMDAL=PMDAR bits = “0”).
AK4675
DSP or
μ
P
MCKI
BICK
LRCK
SDTO
SDTI
BCLK
LRCK
SDTI
SDTO
MCKO
1fs
32fs or 64fs
MCLK
256fs, 384fs, 512fs,
768fs or 1024fs
Figure 43. EXT Master Mode
BCKO bit
BICK Output Frequency
0 32fs
(default)
1 64fs
Table 15. BICK Output Frequency at Master Mode