AK4671_10 Datasheet, PDF (49/166 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/RCV/HP-AMP

[AK4671]
■ EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
When PMPLL bit is “0”, the AK4671 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 the
AK4671 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 FS2-0 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.
Mode
0
1
4
5
6
7
Others
FS3 bit
FS2 bit FS1 bit FS0 bit
MCKI Input
Frequency
Sampling Frequency
Range
x
0
0
0
256fs
8kHz ∼ 48kHz
x
0
0
1
1024fs
8kHz ∼ 13kHz
x
1
0
0
384fs
8kHz ∼ 48kHz
x
1
0
1
768fs
8kHz ∼ 26kHz
x
1
1
0
512fs
8kHz ∼ 26kHz
x
1
1
1
256fs
8kHz ∼ 48kHz
(default)
Others
N/A
N/A
(x: Don’t care, N/A: Not available)
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 reduced 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.
MCKI
S/N
(fs=8kHz, 20kHzLPF + A-weighted)
256fs, 384fs
83dB
512fs, 768fs
93dB
1024fs
93dB
Table 12. 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 = “1” or PMDAR bit = “1”). If MCKI is not provided, the AK4671 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”).
AK4671
MCKO
MCKI
BICK
LRCK
SDTO
SDTI
256fs, 384fs, 512fs,
768fs or 1024fs
DSP or μP
MCLK
≥ 32fs
BCLK
1fs
LRCK
SDTI
SDTO
Figure 43. EXT Slave Mode
MS0666-E-02
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2010/06