[AK4675]
■ EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
When PMPLL bit is “0”, the AK4675 becomes EXT mode. Master clock is input from the MCKI pin, the internal PLL
circuit is not operated. This mode is compatible with I/F of the normal audio CODEC. The clocks required to operate are
MCKI (256fs, 384fs, 512fs, 768fs or 1024fs), LRCK (fs) and BICK (≥32fs). The master clock (MCKI) should be
synchronized with LRCK. The phase between these clocks does not matter. The input frequency of MCKI is selected by
FS1-0 bits (Table 11).
In case that the CODEC is used without Audio I/F (like phone call), the CODEC can be operated by MCKI only. In this
case, BICK and LRCK can be stopped.
MCKI Input
Frequency
Sampling Frequency
Range
Mode
FS3 bit
FS2 bit
FS1 bit
FS0 bit
x
0
1
4
5
6
7
0
0
1
1
1
1
0
0
0
0
1
1
0
1
0
1
0
1
256fs
1024fs
384fs
768fs
512fs
256fs
N/A
8kHz ∼ 48kHz
8kHz ∼ 13kHz
8kHz ∼ 48kHz
8kHz ∼ 26kHz
8kHz ∼ 26kHz
8kHz ∼ 48kHz
N/A
x
x
x
x
x
(default)
Others
Others
(N/A: Not available, x: Don’t care)
Table 11. MCKI Frequency at EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
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 12.
S/N
MCKI
(fs=8kHz, 20kHzLPF + A-weighted)
256fs
512fs
1024fs
83dB
93dB
93dB
Table 12. Relationship between MCKI and S/N of LOUT1/ROUT1 pins
The external clocks (MCKI, BICK and LRCK) should always be present whenever the ADC or DAC is in operation
(PMADL bit = “1”, PMADR bit = “1”, PMDAL bit = “1” or PMDAR bit = “1”). If these clocks are not provided, the
AK4675 may draw excess current and it is not possible to operate properly because utilizes dynamic refreshed logic
internally. If the external clocks are not present, the ADC and DAC should be in the power-down mode
(PMADL=PMADR=PMDAL=PMDAR bits = “0”).
AK4675
MCKO
DSP or μP
256fs, 384fs, 512fs,
768fs or 1024fs
MCKI
BICK
LRCK
MCLK
BCLK
LRCK
≥ 32fs
1fs
SDTI
SDTO
SDTI
SDTO
Figure 42. EXT Slave Mode
MS0963-E-00
2008/05
- 57 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
