CS2200-OT Datasheet, PDF (12/23 Pages) Cirrus Logic – Fractional-N Frequency Synthesizer

CS2200-OTP
Selection of the user defined ratio from the four stored ratios is made by using the M[1:0] pins.
Referenced Control
Parameter Definition
M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 14
5.3.4 Ratio Configuration Summary
The R_UD is the user defined ratio for which up to four different values (Ratio_0-3) can be stored in the one
time programmable memory. The M[1:0] pins then select the user defined ratio to be used as well as the
modal configuration set. R-Mod is applied accordingly. The user defined ratio and ratio modifier make up
the effective ratio R_EFF, the final calculation used to determine the output to input clock ratio. The effective
ratio is then corrected for the internal dividers. The conceptual diagram in Figure 6 summarizes the fea-
tures involved in the calculation of the ratio values used to generate the fractional-N value which controls
the Frequency Synthesizer. The subscript ‘4’ indicates the modal parameters.
Effective Ratio REFF
M[1:0] pins
User Defined Ratio RUD
Ratio 0
Ratio 1
Ratio 2
Ratio Format
12.20
Ratio 3
Timing Reference Clock
(XTI/REF_CLK)
M2 pin
RModSel[1:0]4
RefClkDiv[1:0]
Ratio
Modifier
R Correction
Divide
RefClkDiv[1:0]
SysClk
Static Ratio, ‘N’
Frequency
Synthesizer
PLL Output
Figure 6. Ratio Feature Summary
Referenced Control
Parameter Definition
Ratio 0-3................................“Ratio 0 - 3” on page 18
M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 14
RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 17
RefClkDiv[1:0] .......................“Reference Clock Input Divider (RefClkDiv[1:0])” on page 18
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