Datasheet

Section 21 Clock Pulse Generator
Rev. 3.00 Mar 17, 2006 page 814 of 926
REJ09B0283-0300
21.2 Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
21.2.1 Connecting a Crystal Resonator
A crystal resonator can be connected as shown in the example in figure 21.2. Select the damping
resistance R
d
according to table 20.1. An AT-cut parallel-resonance type should be used.
Figure 21.3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has
the characteristics shown in table 21.2. When a crystal resonator is used, the range of its
frequencies is from 8 to 25 MHz.
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF
Figure 21.2 Connection of Crystal Resonator (Example)
Table 21.1 Damping Resistance Value
Frequency (MHz) 8 12 16 20 25
R
d
(Ω) 2000000
XTAL
C
L
AT-cut parallel-resonance type
EXTAL
C
0
LR
s
Figure 21.3 Crystal Resonator Equivalent Circuit