AK4649 Datasheet, PDF (29/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
■ EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
When PMPLL bit is “0”, the AK4649 becomes EXT mode. Master clock can directly be inputted from the MCKI pin,
without the internal PLL circuit operation. This mode is compatible with I/F of the normal audio CODEC. The clocks
required to operate this mode are MCKI (256fs, 512fs or 1024fs), LRCK (fs) and BICK (≥32fs). The master clock
(MCKI) must 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).
Mode
FS3-2 bits
FS1 bit FS0 bit
MCKI Input
Frequency
Sampling Frequency
Range
0
x
0
0
256fs
7.35kHz ∼ 48kHz
1
x
0
1
1024fs
7.35kHz ∼ 13kHz
2
x
1
0
512fs
7.35kHz ∼ 26kHz
3
x
1
1
256fs
7.35kHz ∼ 48kHz
Others
Others
N/A
N/A
Table 11. MCKI Frequency at EXT Slave Mode (PMPLL bit = “0”, M/S bit = “0”)
(x: Don’t care, N/A: Not Available)
(default)
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.
MCKI
S/N
(fs=8kHz, 20kHzLPF + A-weighted)
256fs
83dB
512fs
95dB
1024fs
96dB
Table 12. Relationship between MCKI and S/N of LOUT/ROUT pins
The external clocks (MCKI, BICK and LRCK) must always be present whenever the ADC, DAC or Programmable Filter
is in operation (PMADL bit = “1”, PMADR bit = “1”, PMDAC bit = “1” or PMPFIL bit = “1”). If these clocks are not
provided, the AK4649 may draw excess current and it is not possible to operate properly because utilizes dynamic
refreshed logic internally. When the external clocks are not present, the ADC and DAC should be in the power-down
mode (PMADL=PMADR=PMDAC = PMPFIL bits = “0”).
AK4649
MCKO
MCKI
BICK
LRCK
SDTO
SDTI
256fs, 512fs or 1024fs
DSP or μP
MCLK
≥ 32fs
BCLK
1fs
LRCK
SDTI
SDTO
Figure 18. EXT Slave Mode
MS1023-E-01
- 29 -
2010/08