MC9S12Q FREESCALE [Freescale Semiconductor, Inc], MC9S12Q Datasheet - Page 618

• Manufacturer Part Number: MC9S12Q
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Appendix A Electrical Characteristics
A.4.3
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.4.3.1
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:
The phase detector relationship is given by:
i
618
ch
is the current in tracking mode.
OSC
1
, f
1
= 4MHz and a 16MHz bus clock.
f
and i
osc
Phase Locked Loop
XFC Component Selection
ch
from
refdv+1
K
V
1
Table
=
K
K
A-17.
f
ref
1
=
Figure A-2. Basic PLL Functional Diagram
V
e
DDPLL
–
---------------------- -
f
K
i
1
ch
1
–
D
f
1V
VCO
f
vco
cmp
K
Cp
=
Cs
V
= 50MHz and f
MC9S12Q128
–
Detector
Loop Divider
Phase
100
Rev 1.09
synr+1
KF
R
1
e
= 316.7Hz/
--------------------- -
60 50
–
100
–
ref
= 1MHz. E.g., these frequencies are used
XFC Pin
= -90.48MHz/V
1
2
VCO
KV
Freescale Semiconductor
f
vco