MC9S12A256B ETC, MC9S12A256B Datasheet - Page 109

• Manufacturer Part Number: MC9S12A256B
• Description: device made up of standard HCS12 blocks and the HCS12 processor core
• Manufacturer: ETC

A.5.3 Phase Locked Loop
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.5.3.1 XFC Component Selection
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 VCO Gain at the desired VCO output frequency is approximated by:
The phase detector relationship is given by:
i
ch
is the current in tracking mode.
1
, f
1
and i
f
osc
ch
from Table A-16.
refdv+1
Figure A-2 Basic PLL functional diagram
Freescale Semiconductor, Inc.
1
For More Information On This Product,
f
ref
K
Go to: www.freescale.com
K
V
=
=
K
1
–
f
cmp
i
ch
e
Loop Divider
---------------------- -
Detector
f
K
Phase
1
synr+1
1
–
K
K
MC9S12DP256B Device User Guide — V02.14
f
V
1V
1
vco
C
s
VDDPLL
R
1
2
C
p
VCO
K
V
f
vco
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