[AK4646]
■ EXT Master Mode (PMPLL bit = “0”, M/S bit = “1”)
The AK4646 becomes EXT Master Mode by setting PMPLL bit = “0” and M/S bit = “1”. Master clock is input from
MCKI pin, the internal PLL circuit is not operated. The clock required to operate is MCKI (256fs, 512fs or 1024fs). The
input frequency of MCKI is selected by FS1-0 bits (Table 13).
MCKI Input
Frequency
Sampling Frequency
Range
Mode
FS3-2 bits
FS1 bit
FS0 bit
Don’t care
Don’t care
Don’t care
Don’t care
0
1
2
3
0
0
1
1
0
1
0
1
256fs
1024fs
256fs
512fs
(default)
7.35kHz ∼ 48kHz
7.35kHz ∼ 13kHz
7.35kHz ∼ 48kHz
7.35kHz ∼ 26kHz
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 LOUT/ROUT pins at fs=8kHz is shown in Table 14.
S/N
MCKI
(fs=8kHz, 20kHzLPF + A-weighted)
256fs
512fs
1024fs
83dB
93dB
93dB
Table 14. Relationship between MCKI and S/N of LOUT/ROUT pins
MCKI should always be present whenever the ADC or DAC is in operation (PMADL bit = “1”, PMADR bit = “1” or
PMDAC bit = “1”). If MCKI is not provided, the AK4646 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=PMDAC bits = “0”).
AK4646
MCKO
DSP or μP
256fs, 512fs or 1024fs
MCKI
BICK
LRCK
MCLK
BCLK
LRCK
32fs or 64fs
1fs
SDTI
SDTO
SDTI
SDTO
Figure 17. EXT Master Mode
BICK Output
BCKO bit
Frequency
0
1
32fs
64fs
(default)
Table 15. BICK Output Frequency at Master Mode
MS0557-E-05
2011/01
- 26 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
