MC9S12E32CFU FREESCALE [Freescale Semiconductor, Inc], MC9S12E32CFU Datasheet - Page 577

• Manufacturer Part Number: MC9S12E32CFU
• Description: HCS12 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

K
A.3.3
The oscillator provides the reference clock for the PLL. The PLL´s Voltage Controlled Oscillator (VCO)
is also the system clock source in self clock mode.
A.3.3.1
This section describes the selection of the XFC components to achieve a good filter characteristics.
The following procedure can be used to calculate the resistance and capacitance values using typical values
for K
The grey boxes show the calculation for f
for f
The VCO Gain at the desired VCO frequency is approximated by:
K
The phase detector relationship is given by:
i
Freescale Semiconductor
ch
V
is the current in tracking mode.
OSC
=
1
=
, f
K
1
–
= 4MHz and a 25MHz bus clock.
and i
1
i
ch
Phase Locked Loop
XFC Component Selection
e
ch
----------------------- -
f
K
K
from
1
f
1
–
osc
V
f
1V
vco
Table
=
–
refdv+1
A-13.
100
= 316.7Hz/
1
Figure A-2. Basic PLL functional diagram
e
MC9S12E128 Data Sheet, Rev. 1.07
----------------------
f
60 50
ref
VDDPLL
–
VCO
100
–
= 50MHz and f
= -90.48MHz/V
f
cmp
C
C
p
Loop Divider
s
Detector
Phase
synr+1
K
ref
1
R
= 1MHz. E.g., these frequencies are used
XFC Pin
Appendix A Electrical Characteristics
1
2
VCO
K
V
f
vco
577