mc68hc908gr8b Freescale Semiconductor, Inc, mc68hc908gr8b Datasheet - Page 71

• Manufacturer Part Number: mc68hc908gr8b
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

4.8.3 Choosing a Filter
As described in
stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply
voltage.
Figure 4-10
the PLL are not critical, the three component filter network shown in
single capacitor, C
at various reference frequencies. For reference frequencies between the values listed in the table,
extrapolate to the nearest common capacitor value. In general, a slightly larger capacitor provides more
stability at the expense of increased lock time.
Freescale Semiconductor
shows two types of filter circuits. In low-cost applications, where stability and reaction time of
4.8.2 Parametric Influences on Reaction
F
1 MHz
2 MHz
3 MHz
4 MHz
5 MHz
6 MHz
7 MHz
8 MHz
f
, as shown in
RCLK
(A)
CGMXFC
Table 4-4. Example Filter Component Values
V
SSA
Figure
C
F
MC68HC908GR8B Data Sheet, Rev. 3.0
8.2 nF
4.7 nF
3.3 nF
2.2 nF
1.8 nF
1.5 nF
1.2 nF
1 nF
C
F1
Figure 4-10. PLL Filter
4-10(A). Refer to
820 pF
470 pF
330 pF
220 pF
180 pF
150 pF
120 pF
100 pF
C
F2
Time, the external filter network is critical to the
Table 4-4
(B)
C
R
F1
CGMXFC
F1
Figure 4-10(B)
R
for recommended filter components
2k
2k
2k
2k
2k
2k
2k
2k
F1
Acquisition/Lock Time Specifications
V
SSA
C
F2
6.8 nF
5.6 nF
4.7 nF
3.9 nF
3.3 nF
2.7 nF
2.2 nF
18 nF
C
can be replaced by a
F
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