CL
L
Rs
XTAL
EXTAL
C0
AT-cut parallel resonating crystal
Figure 6.3 Equivalent Circuit of External Crystal
Table 6.2 External Crystal Parameters
Frequency (MHz)
Rd max (Ω)
C0 (pF)
2
4
8
10
70
12
60
16
50
500
120
80
7 pF max 7 pF max 7 pF max 7 pF max 7 pF max 7 pF max
Use a crystal with the same frequency as the desired system clock frequency (ø).
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 6.4. The crystal and its load capacitors should be placed as close as possible to the XTAL
and EXTAL pins.
Not allowed
Signal A
Signal B
CL2
XTAL
EXTAL
CL1
Figure 6.4 Board Design around External Crystal
98
RENESAS [ RENESAS TECHNOLOGY CORP ]
