mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 79

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Temperature and processing also can affect acquisition time because the electrical characteristics of the
PLL change. The part operates as specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of the PLL. These factors include
noise injected into the PLL through the filter capacitor, filter capacitor leakage, stray impedances on the
circuit board, and even humidity or circuit board contamination.
5.8.3 Choosing a Filter
As described in
stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply
voltage.
Either of the filter networks in
Figure 5-10
applications where stability is not critical.
Freescale Semiconductor
(a) is used for applications requiring better stability.
5.8.2 Parametric Influences on Reaction
Figure 5-10
0.033 µF
10 kΩ
CGMXFC
MC68HC908GP32 Data Sheet, Rev. 10
(a)
Figure 5-10. PLL Filter
V
is recommended when using a 32.768kHz reference crystal.
SSA
0.01 µF
Time, the external filter network is critical to the
CGMXFC
Figure 5-10
V
SSA
(b)
0.47 µF
Acquisition/Lock Time Specifications
(b) is used in low-cost
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