(2) Crystal Oscillator: The external crystal should have the characteristics listed in table 8-1.
Table 8-1 External Crystal Parameters
(3) Note on Board Design: When an external crystal is connected, other signal lines should be
kept away from the crystal circuit to prevent induction from interfering with correct
oscillation. See figure 8-4.
When the board is designed, the crystal and its load capacitors should be placed as close as
possible to the XTAL and EXTAL pins.
EXTAL
C
XTAL
L1
CL2 C =C =10 to 22pFL1 L2
CL
XTAL EXTAL
LR
S
C0
AT-cut parallel resonating crystal
Frequency (MHz) 248121620
Rs max (Ω) 500 120 60 40 30 20
C
0 (pF) 7pF max
Figure 8-2 Connection of Crystal Oscillator (Example)
Figure 8-3 Crystal Oscillator Equivalent Circuit
136
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