wm8580a Wolfson Microelectronics plc, wm8580a Datasheet - Page 57

• Manufacturer Part Number: wm8580a
• Description: Multichannel Codec With S/pdif Transceiver
• Manufacturer: Wolfson Microelectronics plc

Production Data
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Table 51 PLL S/PDIF Receiver Mode Clock Divider Configuration
PLL CONFIGURATION EXAMPLE
Consider the situation where the oscillator clock (OSCCLK) input frequency is fixed at 12MHz and
the required PLLBCLK frequency is 12.288MHz.
The value of PLLB_N is the integer (whole number) value of R, ignoring all digits to the right of the
decimal point. In this case, R is 8.192, hence PLLB_N is 8.
The PLLB_K value is simply the integer value of (2
A number of example configurations are shown in Table 52. Many other configurations are possible;
Table 52 shows only a small number of valid possibilities. As both PLLs are identical, the same
configuration procedure applies for both.
Table 50 PLL User Mode Clock Divider Configuration
1.
The PLL is designed to operate with best performance when the f
The necessary PLLBCLK frequency is 12.288MHz. Choose POSTSCALE_B and FREQMODE_B
values to set the f
(POSTSCALE_B = 0 and FREQMODE_B[1:0] = 10) will configure the f
and hence will set the f
hence acceptable.
2.
Using the relationship: R = (f
3.
4.
FREQMODE_x[1:0]
POSTSCALE_A
Calculate the f
•
•
•
Calculate R Value
Calculate PLLB_N Value
Calculate PLL_K Value
POSTSCALE_B = 0
FREQMODE_B [1:0] = 10b
f
•
•
•
•
•
•
2
00
01
10
11
= 98.304MHz
0
1
R = (f
R = (98.304 ÷ 12)
R = 8.192
PLLB_K = integer part of (2
PLLB_K = integer part of 805306.368
PLLB_K = 805306 (decimal) / C49BA (hex)
2
2
, FREQMODE_B and POSTSCALE_B Values
2
frequency in the range of 90 to 100MHz. In this case, the default values
÷ f
2
frequency at 98.304MHz; this value is within the 90 to 100MHz range and is
1
)
2
÷ f
1
), the value of R can be calculated.
f
2
TO PLLxCLK DIVISION FACTOR
÷12
÷2
÷4
÷8
0
PLLACLK FREQUENCY
22
POSTSCALE_x
x (8.192 – 8))
22
256fs
128fs
(R-PLLB_N)).
÷16
÷24
÷4
÷8
1
2
clock is between 90 and 100MHz.
2
to PLLBCLK divider as 8
PD, Rev 4.7, March 2009
WM8580
57