ADAU1381 Datasheet, PDF (44/84 Pages) Analog Devices – Low Noise Stereo Codec with Enhanced Recording and Playback Processing

ADAU1381
CLOCK MANAGEMENT, INTERNAL REGULATOR,
AND PLL CONTROL
Register 16384 (0x4000), Clock Control
The clock control register sets the clocking scheme for the
ADAU1381. The system clock can be generated from either the
PLL or directly from the MCKI (master clock input) pin. Addi-
tionally, the MCKO (master clock output) pin can be configured.
Bits[6:5], MCKO Frequency
These bits set the frequency to be output on MCKO as a multiple
of the base sampling frequency (32×, 64×, 128×, or 256×). The
MCKO pin can be used to provide digital microphones with a clock.
Bit 4, MCKO Enable
This bit enables or disables the MCKO pin.
Bit 3, Clock Source Select
The clock source select bit either routes the MCLK input through
the PLL or bypasses the PLL. When using the PLL, the output of
the PLL is always 1024 × fS, and Bits[2:1] should be set to 11.
PLL parameters can be set in the PLL control register. Inputs
directly from MCKI require an exact clock rate as described in
the Bits[2:1], Input Master Clock Frequency section.
Bits[2:1], Input Master Clock Frequency
The maximum clock speed allowed is 1024 × 48 kHz. These bits set
the expected input master clock frequency for proper clock divider
values in order to output a constant system clock of 256 × fS. When
using the PLL, these bits must always be set to 1024 × fS. When
bypassing the PLL, the external clock frequency on the MCKI pin
must be 256 × fS, 512 × fS, 768 × fS, or 1024 × fS. Table 29
and Table 30 show the relationship between the system clock and
the internal master clock for base sampling frequencies of 44.1
kHz and 48 kHz.
Bit 0, Core Clock Enable
This bit enables the internal master clock to start the IC.
Table 28. Clock Control Register
Bits
7
[6:5]
4
3
[2:1]
0
Description
Reserved
MCKO frequency
00: 32 × fS
01: 64 × fS
10: 128 × fS
11: 256 × fS
MCKO enable
0: disabled
1: enabled
Clock source select
0: direct from MCKI pin
1: PLL clock
Input master clock frequency
00: 256 × fS
01: 512 × fS
10: 768 × fS
11: 1024 × fS
Core clock enable
0: core clock disabled
1: core clock enabled
Table 29. Core Clock Output for fS = 44.1 kHz
MCLK Input Setting
MCLK Input Value
256 × fS
11.2896 MHz
512 × fS
22.5792 MHz
768 × fS
33.8688 MHz
1024 × fS
45.1584 MHz
MCLK Input Divider
1
2
3
4
Table 30. Core Clock Output for fS = 48 kHz
MCLK Input Setting
MCLK Input Value
256 × fS
12.288 MHz
512 × fS
24.576 MHz
768 × fS
36.864 MHz
1024 × fS
49.152 MHz
MCLK Input Divider
1
2
3
4
Rev. 0 | Page 44 of 84
Default
00
0
0
00
0
Core Clock
11.2896 MHz
11.2896 MHz
11.2896 MHz
11.2896 MHz
Core Clock
12.288 MHz
12.288 MHz
12.288 MHz
12.288 MHz