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Section 27 Clock Pulse Generator
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
, given in table 27.1, should be used. An AT-cut parallel-resonance crystal resonator
d
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.
Figure 27.2 Typical Connection to Crystal Resonator
Table 27.1 Damping Resistance Values
Frequency (MHz)
R
(Ω)
d
XTAL
Rev. 1.00 Mar. 12, 2008 Page 1052 of 1178
REJ09B0403-0100
EXTAL
XTAL
R
d
C
L
L
C
0
Figure 27.3 Equivalent Circuit of Crystal Resonator
C
L1
C
C
= C
L2
L1
5
300
R
s
EXTAL
AT-cut parallel-resonance crystal resonator
= 10 to 22 pF
L2
8
200
8.5
0
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