Datasheet

[AK4646]
MS0557-E-06 2011/06
- 26 -
■ 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).
Mode FS3-2 bits FS1 bit FS0 bit
MCKI Input
Frequency
Sampling Frequency
Range
0
Don’t care
0 0 256fs
7.35kHz ∼ 48kHz
(default)
1
Don’t care
0 1 1024fs
7.35kHz ∼ 13kHz
2
Don’t care
1 0 512fs
7.35kHz ∼ 48kHz
3
Don’t care
1 1 256fs
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.
MCKI
S/N
(fs=8kHz, 20kHzLPF + A-weighted)
256fs 83dB
512fs 93dB
1024fs 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
DSP or
μ
P
MCKI
BICK
LRCK
SDTO
SDTI
BCLK
LRCK
SDTI
SDTO
MCKO
1fs
32fs or 64fs
MCLK
256fs, 512fs or 1024fs
Figure 17. EXT Master Mode
BCKO bit
BICK Output
Frequency
0 32fs (default)
1 64fs
Table 15. BICK Output Frequency at Master Mode