CDK2000 Cirrus Logic, Inc., CDK2000 Datasheet - Page 14

• Manufacturer Part Number: CDK2000
• Description: Fractional-n Clock Multiplier with Internal LCO
• Manufacturer: Cirrus Logic, Inc.

14
5.4.4
User Defined Ratio R
Ratio 0
Ratio 1
Ratio 2
Ratio 3
Ratio modifiers which would produce an overflow or truncation of R
the maximum and minimum allowable values for R
input and output clocks as shown in the
Selection of the user defined ratio from the four stored ratios is made by using the M[1:0] pins.
Ratio Configuration Summary
The R
time programmable memory. The M[1:0] pins then select the user defined ratio to be used as well as the
modal configuration set. The resolution/format for the R
The user defined ratio, ratio modifier, and automatic ratio modifier make up the effective ratio R
final calculation used to determine the output to input clock ratio. The conceptual diagram in
summarizes the features 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.
Referenced Control
M[1:0]
Referenced Control
Ratio
M[1:0]
LFRatioCfg
RModSel[1:0]
UD
M[1:0] pins
0-3................................“Ratio 0 - 3” on page 20
pins.............................“M1 and M0 Mode Pin Functionality” on page 16
pins.............................“M1 and M0 Mode Pin Functionality” on page 16
UD
is the user defined ratio for which up to four different values ( Ratio
Effective Ratio R
............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 20
........................“R-Mod Selection (RModSel[1:0])” section on page 19
Ratio Format
LFRatioCfg
12.20
20.12
EFF
Parameter Definition
Parameter Definition
Modifier
Ratio
Figure 10. Ratio Feature Summary
M2 pin
RModSel[1:0]
4
“AC Electrical Characteristics” on page
Frequency Reference Clock
Fractional N Logic
Digital PLL &
(CLK_IN)
EFF
are dictated by the frequency limits for both the
UD
is selectable. R-Mod is applied accordingly.
Dynamic Ratio, ‘N’
LCO
EFF
should not be used. In all cases,
0-3
Synthesizer
Frequency
) can be stored in the one
7.
CS2300-OTP
Figure 10
DS844F1
EFF
PLL Output
, the