Datasheet

Rev.6.00 Oct.28.2004 page 663 of 1016
REJ09B0138-0600H
20.3 Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
20.3.1 Connecting a Crystal Resonator
Circuit Configuration: A crystal resonator can be connected as shown in the example in figure 20-2. Select the damping
resistance R
d
according to table 20-2. An AT-cut parallel-resonance crystal should be used.
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF
Figure 20-2 Connection of Crystal Resonator (Example)
Table 20-2 Damping Resistance Value
Frequency (MHz) 2 4 8 10 12 16 20
R
d
(Ω) 1k 500 200 0 0 0 0
Crystal Resonator: Figure 20-3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has the
characteristics shown in table 20-3 and the same resonance frequency as the system clock (ø).
XTAL
C
L
AT-cut parallel-resonance type
EXTAL
C
0
LR
s
Figure 20-3 Crystal Resonator Equivalent Circuit
Table 20-3 Crystal Resonator Parameters
Frequency (MHz) 2 4 8 10 12 16 20
R
S
max (Ω) 500 120 80 70 60 50 40
C
0
max (pF) 7 7 7 7 7 7 7