wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 104

• Manufacturer Part Number: wm8918
• Description: Ultra Low Power Dac For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8918
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EXAMPLE FLL CALCULATION
To generate 12.288 MHz output (F
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Set FLL_CLK_REF_DIV in order to generate F
FLL_CLK_REF_DIV = 00 (divide by 1)
Set FLL_CTRL_RATE to the recommended setting:
FLL_CTRL_RATE = 000 (divide by 1)
Set FLL_GAIN to the recommended setting:
FLL_GAIN = 0000 (multiply by 1)
Set FLL_OUTDIV for the required output frequency as shown in Table 64:-
F
Set FLL_FRATIO for the given reference frequency as shown in Table 65:
F
Calculate F
F
Calculate N.K as given by N.K = F
N.K = 98.304 / (1 x 12) = 8.192
Determine FLL_N and FLL_K from the integer and fractional portions of N.K:-
FLL_N is 8. FLL_K is 0.192
Confirm that N.K is a fractional quantity and set FLL_FRACN_ENA:
N.K is fractional. Set FLL_FRACN_ENA = 1.
Note that, if N.K is an integer, then an alternative value of FLL_FRATIO should be
selected in order to produce a fractional value of N.K.
OUT
REF
VCO
= 12MHz, therefore FLL_FRATIO = 0h (divide by 1)
= 12.288 MHz, therefore FLL_OUTDIV = 07h (divide by 8)
= 12.288 x 8 = 98.304MHz
VCO
as given by F
OUT
) from a 12.000 MHz reference clock (F
VCO
= F
VCO
OUT
/ (FLL_FRATIO x F
x FLL_OUTDIV:-
REF
<=13.5MHz:
REF
PD, Rev 4.0, September 2010
):
REF
):
Production Data
104