WM8352 datasheet(58/336 Pages) WOLFSON

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WM8352

Production Data

PD, February 2011, Rev 4.4

12.4.1

EXAMPLE FLL CALCULATION

To generate 12.288 MHz output (FOUT) from a 12.000 MHz reference clock (FREF):



Determine FLL_OUTDIV for the required output frequency as given by Table 16:

For FOUT = 12.288 MHz, FLL_OUTDIV = 2h (divide by 8)



Calculate FVCO for the given FLL_OUTDIV:

FVCO = FOUT * FLL_OUTDIV = 12.288 MHz * 8 = 98.304 MHz



Calculate the required N.K x FLL_RATIO for the given FREF and FVCO.:

N.K x FLL_RATIO = FVCO / FREF = 8.192



Determine FLL_REF_FREQ for the given FREF as given by Table 17:

For FREF = 12MHz, FLL_REF_FREQ = 0



Determine FLL_RATIO as given by Table 17:

For High Frequency Reference, FLL_RATIO = 1



Calculate N.K for the given FLL_RATIO:

N.K = 8.192 / 1 = 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



Set FLL_FRAC according to whether fractional mode is required:

FLL_K is 0.192, so fractional mode is required; FLL_FRAC = 1

Note that, for best performance, FLL Fractional Mode should always be used. If the calculations yield

an integer value of N.K, then it is recommended to adjust FLL_RATIO in order to obtain a non-integer

value of N.K.

WM8352 Datasheet(PDF) 58 Page - Wolfson Microelectronics plc