MC68HC908JW32_09 Datasheet, PDF (74/232 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Clock Generator Module (CGM)
5.8.3 Choosing a Filter
As described in 5.8.2 Parametric Influences on Reaction Time, the external filter network is critical to the
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 is recommended when using a 4MHz reference clock
(CGMRCLK). Figure 5-10 (a) is used for applications requiring better stability. Figure 5-10 (b) is used in
low-cost applications where stability is not critical.
CGMXFC
CGMXFC
2 kΩ
2n2 nF
100 pF
0.22 µF
V_SS
V_SS
(a)
(b)
Figure 5-10. PLL Filter
MC68HC908JW32 Data Sheet, Rev. 6
74
Freescale Semiconductor