MC68HC912D60A MOTOROLA [Motorola, Inc], MC68HC912D60A Datasheet - Page 429

• Manufacturer Part Number: MC68HC912D60A
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

21.3.3.2 Particular Case of an 8MHz Synthesis
MC68HC912D60A — Rev 3.0
MOTOROLA
In both equations, the power supply should be 5V. Start with the target
loop bandwidth as a function of the other parameters, but obviously,
nothing prevents the user from starting with the capacitor value for
example. Also, remember that the smoothing capacitor is always
assumed to be one tenth of the series capacitance value.
So with:
m:
R:
C:
F
ζ:
F
for the ‘tracking’ mode:
and for the ‘acquisition’ mode:
Assume that a desired value for the damping factor of the second order
system is close to 0.9 as this leads to a satisfactory transient response.
Then, derived from the equations above,
suggest sets of values corresponding to several loop bandwidth
possibilities in the case of an 8MHz synthesis for the two cases
mentioned above.
bus
c
:
Freescale Semiconductor, Inc.
: the target bus frequency expressed in MHz
For More Information On This Product,
acquisition (AUTO=0, ACQ=0 in the PLLCR register).
the multiplying factor for the reference frequency (i.e. (synr+1))
the series resistance of the low pass filter in Ω
the series capacitance of the low pass filter in nF
the desired damping factor
the desired loop bandwidth expressed in Hz
Appendix: CGM Practical Aspects
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F
F
c
c
=
=
2 10
------------------------ -
2 10
------------------------ -
π R C
π R C
⋅
⋅
⋅
⋅
9
9
⋅
⋅
⋅
⋅
ζ
ζ
2
2
=
=
415.61 e
-------------------------------------------------------- -
37.78 e
----------------------------------------------------- -
⋅
Practical Aspects For The PLL Usage
⋅
2 π m
2 π m
Table 21-1
⎛
⎝
⋅
⋅
⎛
⎝
1.675 F
---------------------------- -
1.675 F
---------------------------- -
Appendix: CGM Practical Aspects
10.795
10.795
⋅
⋅
–
–
bus
bus
⎞
⎠
⎞
⎠
⋅
⋅
R
R
and
Table 21-2
Technical Data
429