AK4951AEN Datasheet, PDF (31/105 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/HP/SPK-AMP

[AK4951A]
■ EXT Master Mode (PMPLL bit = “0”, M/S bit = “1”)
The AK4951A becomes EXT Master Mode by setting PMPLL bit = “0” and M/S bit = “1”. Master clock can
be input to the internal ADC and DAC directly from the MCKI pin without the internal PLL circuit operation.
The external clock required to operate the AK4951A is MCKI (256fs, 384fs, 512fs or 1024fs). The input
frequency of MCKI is selected by CM1-0 bits (Table 14) and the sampling frequency is selected by FS3-0
bits (Table 15). When the state of AK4951A is ADC power-down or Loopback mode, the output of BICK,
LRCK and SDTO pins can be stopped by CKOFF bit. When CKOFF bit = “1”, BICK, LRCK and SDTO
pins output “L”. The BICK output frequency is selected between 32fs or 64fs, by BCKO bit (Table 17).
Table 14. MCKI Frequency at EXT Master Mode (PMPLL bit = “0”, M/S bit = “1”)
Mode CM1 bit CM0 bit MCKI Input Frequency Sampling Frequency Range
0
0
0
256fs
8kHz ≤ fs ≤ 48kHz
(default)
1
0
1
384fs
8kHz < fs ≤ 48kHz
2
1
0
512fs
8kHz < fs ≤ 48kHz
3
1
1
1024fs
8kHz ≤ fs ≤ 24kHz
Mode FS3 bit
0
0
1
0
2
0
5
0
7
0
9
1
10
1
11
1
15
1
Others
(N/A: Not Available)
Table 15. Setting of Sampling Frequency
FS2 bit FS1 bit FS0 bit Sampling Frequency
0
0
0
8kHz mode
0
0
1
12kHz mode
0
1
0
16kHz mode
1
0
1
11.025kHz mode
1
1
1
22.05kHz mode
0
0
1
24kHz mode
0
1
0
32kHz mode
0
1
1
48kHz mode
1
1
1
44.1kHz mode
Others
N/A
(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 reduced by using higher frequency of the master clock.
The S/N of the DAC output through HPL/HPR pins is shown in Table 16.
Table 16. Relationship between MCKI and S/N of HPL/HPR pins
MCKI
S/N (fs=8kHz, 20kHzLPF + A-weighted)
256fs
82dB
384fs
82dB
512fs
95dB
1024fs
97dB
AK4951A
MCKI
BICK
LRCK
SDTO
SDTI
256fs, 384fs,
512fs or 1024fs
32fs or 64fs
1fs
DSP or P
MCLK
BCLK
LRCK
SDTI
SDTO
Figure 18. EXT Master Mode
016001936-E-00
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2016/03