Datasheet

Section 27 Clock Pulse Generator
Rev. 2.00 Aug. 20, 2008 Page 1050 of 1198
REJ09B0403-0200
27.1 Oscillator
Clock pulses can be supplied either by connecting a crystal resonator or by providing external
clock input.
27.1.1 Connecting Crystal Resonator
Figure 27.2 shows a typical method of connecting a crystal resonator. An appropriate damping
resistance R
d
, given in table 27.1, should be used. An AT-cut parallel-resonance crystal resonator
should be used.
Figure 27.3 shows the equivalent circuit of a crystal resonator. A crystal resonator having the
characteristics given in table 27.2 should be used.
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF
Figure 27.2 Typical Connection to Crystal Resonator
Table 27.1 Damping Resistance Values
Frequency (MHz) 5 8 8.5
R
d
(Ω) 300 200 0
XTAL
C
L
AT-cut parallel-resonance crystal resonator
EXTAL
C
0
LR
s
Figure 27.3 Equivalent Circuit of Crystal Resonator