[AK4634]
■ EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
When PMPLL bit is “0”, the AK4634 becomes EXT Slave 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, 512fs or 1024fs), FCK (fs) and BICK (≥32fs). The master clock (MCKI) should be synchronized with
FCK. The phase between these clocks is not important. The input frequency of MCKI is selected by FS1-0 bits. (Table 11)
Mode
FS3-2 bits
FS1 bit
FS0 bit
MCKI Input
Frequency
256fs
Sampling Frequency
Range
x
x
x
x
0
1
0
1
(default)
0
1
2
3
0
0
1
1
7.35kHz ≤ fs ≤ 48kHz
7.35kHz ≤ fs ≤ 13kHz
7.35kHz ≤ fs ≤ 26kHz
7.35kHz ≤ fs ≤ 48kHz
1024fs
512fs
256fs
Table 11. MCKI Frequency at EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”) (x: Don’t care)
External Slave Mode does not support Mode 0 (DSP Mode) of Audio Interface Format.
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. (Table 12, Table 13)
S/N (fs=8kHz, 20kHzLPF + A-weighted)
MCKI
DAC →AOUT
256fs
512fs
1024fs
84dB
92dB
92dB
Table 12. Relationship between MCKI and S/N of AOUT and SPK-Amp
Output Noise Level
(SVDD=3.3V,fs=8kHz, 20kHzLPF + A-weighted)
MCKI
SDTI → SPK-Amp
-58dBV
256fs
512fs
-72dBV
1024fs
-80dBV
Table 13. Relationship between MCKI and Output Noise Level of SPK-Amp
The external clocks (MCKI, BICK and FCK) should always be present whenever the ADC or DAC or SPK or
Programmable Filter is in operation (PMADC = PMDAC = PMSPK bit = PMPFIL bits = “1”). If these clocks are not
provided, the AK4634 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, DAC, SPK and Programmable Filter should be
in the power-down mode (PMADC = PMDAC = PMSPK bit = PMPFIL bits = “0”).
AK4634
MCKO
DSP or μP
256fs, 512fs or 1024fs
MCKI
BICK
FCK
MCLK
BCLK
FCK
≥ 32fs
1fs
SDTI
SDTO
SDTI
SDTO
Figure 23. EXT Slave Mode
MS0983-E-00
2008/07
- 29 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
