Datasheet

Section 23 Clock Pulse Generator
Rev. 4.00 Jun 06, 2006 page 672 of 1004
REJ09B0301-0400
23.3 Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
23.3.1 Connecting a Crystal Resonator
Circuit Configuration: A crystal resonator can be connected as shown in the example in figure
23.2. Select the damping resistance R
d
according to table 23.2. An AT-cut parallel-resonance
crystal should be used.
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22pF
Figure 23.2 Connection of Crystal Resonator (Example)
Table 23.2 Damping Resistance Value
Frequency (MHz)24810121620
R
d
(Ω) 1k5002000000
Crystal resonator: Figure 23.3 shows the equivalent circuit of the crystal resonator. Use a crystal
resonator that has the characteristics shown in table 23.3 and the same frequency as the system
clock (φ).
XTAL
C
L
AT-cut parallel-resonance type
EXTAL
C
0
LR
s
Figure 23.3 Crystal Resonator Equivalent Circuit