CDK2000 Cirrus Logic, Inc., CDK2000 Datasheet - Page 13

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

DS844F1
5.4
5.4.1
5.4.2
5.4.3
Output to Input Frequency Ratio Configuration
User Defined Ratio (R
The User Defined Ratio, R
desired input to output clock ratio. Up to four different ratios, Ratio
time programmable memory. Selection between the four ratios is achieved by the M[1:0] mode select
pins. The 32-bit R
format selectable by the LFRatioCfg global parameter.
The R
tion with the remaining 20 LSBs representing the fractional binary portion. The maximum multiplication
factor is approximately 4096 with a resolution of 0.954 PPM in this configuration. See
User Defined Ratio” on page 22
The R
portion with the remaining 12 LSBs representing the fractional binary portion. In this configuration, the
maximum multiplication factor is approximately 1,048,575 with a resolution of 244 PPM. It is recommend-
ed that the 12.20 High-Resolution format be utilized whenever the desired ratio is less than 4096 since
the output frequency accuracy of the PLL is directly proportional to the accuracy of the timing reference
clock and the resolution of the R
Ratio Modifier (R-Mod)
The Ratio Modifier is used to internally multiply/divide the currently addressed R
register space remain unchanged). The available options for R-Mod are summarized in
page
global parameter (see
Effective Ratio (R
The Effective Ratio (R
previously described. R
R
Referenced Control
Ratio
LFRatioCfg
M[1:0]
Referenced Control
Ratio
RModSel[1:0]
M2Config[2:0]........................“M2 Pin Configuration (M2Config[2:0])” on page 21
EFF
0-3................................“Ratio 0 - 3” on page 20
0-3................................“Ratio 0 - 3” on page 20
13. R-Mod is enabled via the M2 pin in conjunction with the appropriate setting of the M2Config[2:0]
= R
....................................“M1 and M0 Mode Pin Functionality” on page 16
UD
UD
UD
for high resolution (12.20) format is encoded with 12 MSBs representing the integer binary por-
for high multiplication (20.12) format is encoded with 20 MSBs representing the integer binary
............................“Low-Frequency Ratio Configuration (LFRatioCfg)” on page 20
........................“R-Mod Selection (RModSel[1:0])” section on page 19
•
R-Mod
UD
can be expressed in either a high resolution (12.20) or high multiplication (20.12)
EFF
EFF
Section 5.7.2 on page
Parameter Definition
Parameter Definition
EFF
RModSel[1:0]
) is an internal calculation comprised of R
UD
)
is calculated as follows:
UD
, is a 32-bit un-signed fixed-point number which determines the basis for the
)
00
01
10
11
UD
for more information.
.
Table 2. Ratio Modifier
17).
R Modifier
0.0625
0.125
0.25
0.5
0-3
UD
, can be stored in the CS2300’s one
and the appropriate modifiers, as
UD
( Ratio
CS2300-OTP
“Calculating the
0-3
stored in the
Table 2 on
13