MC68HC12 MOTOROLA [Motorola, Inc], MC68HC12 Datasheet - Page 449

• Manufacturer Part Number: MC68HC12
• Description: The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit
• Manufacturer: MOTOROLA [Motorola, Inc]

23.3.3.2 Particular Case of an 8MHz Synthesis
MC68HC912DT128A — Rev 4.0
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
:
: the target bus frequency expressed in MHz
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
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 23-1
⎛
⎝
⋅
⋅
⎛
⎝
1.675 F
---------------------------- -
1.675 F
---------------------------- -
Appendix: CGM Practical Aspects
10.795
10.795
⋅
⋅
–
–
bus
bus
⎞
⎠
⎞
⎠
⋅
⋅
R
R
and
Table 23-2
Technical Data
449