CS2000-OTP

18

DS758PP1

5.4.7

Ratio Configuration Summary

time programmable memory. The M[1:0] pins or LockClk[1:0] modal parameter then select the user de-

fined ratio to be used (depending on if static or dynamic ratio mode is to be used). The resolution for the

is only available in dynamic mode. The user defined ratio, ratio modifier, and automatic ratio modifier

effective ratio is then corrected for the internal dividers. The frequency synthesizer’s fractional-N source

selection is made between the static ratio (in frequency synthesizer mode) or the dynamic ratio generated

from the digital PLL (in Hybrid PLL mode) by either the FracNSrc modal parameter for manual mode or

the presence of CLK_IN in automatic mode. The conceptual diagram in Figure 12 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.

Figure 12. Ratio Feature Summary

Referenced Control

Parameter Definition

Ratio 0-3................................“Ratio 0 - 3” on page 24

M[1:0] pins.............................“M1 and M0 Mode Pin Functionality” on page 20

LockClk[1:0] ..........................“Lock Clock Ratio (LockClk[1:0])” section on page 24

LFRatioCfg ............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 26

RModSel[1:0] ........................“R-Mod Selection (RModSel[1:0])” section on page 23

AutoRMod .............................“Auto R-Modifier Enable (AutoRMod)” on page 24

RefClkDiv[1:0] .......................“Reference Clock Input Divider (RefClkDiv[1:0])” on page 25

FracNSrc ...............................“Fractional-N Source for Frequency Synthesizer (FracNSrc)” section on page 24

Ratio Format

Frequency Reference Clock

(CLK_IN)

SysClk

PLL Output

Frequency

Synthesizer

Digital PLL &

Fractional N Logic

R Correction

N

Ratio 0

Ratio 1

Ratio 2

Ratio 3

12.20

20.12

12.20

only

M[1:0] pins

LFRatioCfg

Ratio

Modifier

Ratio

Modifier

Auto

R-Mod

or M2 pin

FsDet[1:0]

Auto Selection

(CLK_IN sense)

Manual Selection

R Correction

RefClkDiv[1:0]

Timing Reference Clock

(XTI/REF_CLK)

Divide

RefClkDiv[1:0]

Static Ratio

Dynamic Ratio

M2 pin force Manual

or

M[1:0] pins =? LockClk[1:0]

≠

=

M2 pin