WM9714CLGEFLSLASHV datasheet(23/120 Pages) CIRRUS

23 / 120 page

WM9714L

Rev 4.0

INTEGER N MODE

The nominal output frequency of the PLL (PLL_OUT) is 98.304MHz which is divided by 4 to achieve a

nominal system clock of 24.576MHz.

The integer division ratio (N) is determined by: FPLL_out / FPLL_IN , and is set by N[3:0] and must be in the

range 5 to 12 for integer N operation (0101 = div by 5, 1100 = div by 12). Note that setting LF=1

enables a further division by 4 required for input frequencies in the range 2.048MHz

– 4.096MHz.

Integer N mode is selected by setting SDM=0.

FRACTIONAL N MODE

Fractional N mode provides a divide resolution of 1/222 and is set by K[21:0] (register 46h, see

section). The relationship between the required division X, the fractional division K[21:0] and the

integer division N[3:0] is:







 22

where 0 < (X

– N) < 1 and K is rounded to the nearest whole number.

For example, if the PLL_IN clock is 13MHz and the desired PLL_OUT clock is 98.304MHz then the

desired division, X, is 7.5618. So N[3:0] will be 7h and K[21:0] will be 23F488h to produce the desired

98.304MHz clock (see Table 5).

INPUT CLOCK (PLL_IN)

DESIRED

PLL

OUTPUT

(PLL_OUT)

DIVISION

REQUIRED

(X)

FRACTIONAL

DIVISION (K)

INTEGER

DIVISION (N)

2.048MHz

98.304MHz

12x4*

4.096MHz

98.304MHz

6x4*

12.288MHz

98.304MHz

13MHz

98.304MHz

7.5618

0.5618

27MHz (13.5MHz)**

98.304MHz

7.2818

0.2818

*Divide by 4 enabled in PLL feedback path for low frequency inputs. (LF = 1)

**Divide by 2 enabled at PLL input for frequencies > 14.4MHz > 38MHz (DIVSEL = 1, DIVCTL = 0)

Table 5 PLL Modes of Operation

WM9714CLGEFL/V Datasheet(PDF) 23 Page - Cirrus Logic

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