MC68HC908LJ12 Datasheet, PDF (128/413 Pages) Freescale Semiconductor, Inc – 8-bit microcontroller units

Clock Generator Module (CGM)
8.9.3 Choosing a Filter
As described in 8.9.2 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 8-10 is recommended when using
a 32.768kHz reference clock (CGMRCLK). Figure 8-10 (a) is used for
applications requiring better stability. Figure 8-10 (b) is used in low-cost
applications where stability is not critical.
CGMXFC
CGMXFC
10 kΩ
0.033 µF
0.01 µF
0.47 µF
V_SSA
(a)
V_SSA
(b)
Figure 8-10. PLL Filter
MC68HC908LJ12 — Rev. 2.1
Freescale Semiconductor
Clock Generator Module (CGM)
Technical Data
129