Datasheet

AUDIO CLOCK GENERATION
K*R/P
2/Q
PLL_CLKIN
CODEC
CODEC_CLKIN
PLL_OUT
K = J.D
J = 1,2,3,…..,62,63
D= 0000,0001,….,9998,9999
R= 1,2,3,4,….,15,16
P= 1,2,….,7,8
Q=2,3,…..,16,17
MCLK BCLK
CLKDIV_IN PLL_IN
WCLK= Fsref/Ndac
ADC_FSDAC_FS
Ndac=1,1.5,2,…..,5.5,6
DAC DRA => Ndac = 0.5
CODEC_CLK=256*Fsref
CLKDIV_OUT
1/8
PLLDIV_OUT
CLKDIV_CLKIN
TLV320AIC31
SLAS497C – AUGUST 2006 – REVISED DECEMBER 2008 ............................................................................................................................................. www.ti.com
The audio converters in the TLV320AIC31 need an internal audio master clock at a frequency of 256 × F
Sref
,
which can be obtained in a variety of manners from an external clock signal applied to the device.
A more detailed diagram of the audio clock section of the TLV320AIC31 is shown in Figure 23 .
Figure 23. Audio Clock Generation Processing
The part can accept an MCLK input from 512 kHz to 50 MHz, which can then be passed through either a
programmable divider or a PLL, to get the proper internal audio master clock needed by the part. The BCLK
input can also be used to generate the internal audio master clock.
A primary concern is proper operation of the codec at various sample rates with the limited MCLK frequencies
available in the system. This device includes a highly programmable PLL to accommodate such situations easily.
The integrated PLL can generate audio clocks from a wide variety of possible MCLK inputs, with particular focus
paid to the standard MCLK rates already widely used.
When the PLL is disabled,
F
Sref
= CLKDIV_IN / (128 × Q)
Where Q = 2, 3, … , 17
CLKDIV_IN can be MCLK or BCLK, selected by Page 0, register 102, bits D7-D6.
NOTE: When NDAC = 1.5, 2.5, 3.5, 4.5, or 5.5, odd values of Q are not allowed. In this mode, MCLK can be as
high as 50 MHz, and F
Sref
should fall within 39 kHz to 53 kHz.
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