CS2300-CP Datasheet, PDF (18/32 Pages) Cirrus Logic – Fractional-N Clock Multiplier with Internal LCO

5.3.5
CS2300-CP
Ratio Configuration Summary
The R_UD is the user defined ratio stored in the register space. The resolution for the R_UD is selectable by
setting LFRatioCfg. R-Mod is applied if selected. The user defined ratio, ratio modifier, and automatic ratio
modifier make up the effective ratio R_EFF, the final calculation used to determine the output to input clock
ratio. The conceptual diagram in Figure 12 summarizes the features involved in the calculation of the ratio
values used to generate the fractional-N value which controls the Frequency Synthesizer.
LCO
Effective Ratio REFF
Frequency
Synthesizer
PLL Output
User Defined Ratio RUD
Ratio
Ratio Format
12.20
20.12
RModSel[2:0]
Ratio
Modifier
Auto
R-Mod
N
Digital PLL &
Fractional N Logic
LFRatioCfg
AutoRMod
FsDet[1:0]
Frequency Reference Clock
(CLK_IN)
Figure 12. Ratio Feature Summary
Referenced Control
Register Location
Ratio......................................“Ratio (Address 06h - 09h)” on page 27
LFRatioCfg ............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 28
RModSel[2:0] ........................“R-Mod Selection (RModSel[2:0])” section on page 25
AutoRMod .............................“Auto R-Modifier Enable (AutoRMod)” on page 25
FsDet[1:0]..............................“PLL Input Sample Rate Indicator (FsDet[1:0]) - Read Only” section on page 24
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DS843PP1