Datasheet

Section 23 Clock Pulse Generator
Rev. 2.00 Sep. 28, 2009 Page 768 of 870
REJ09B0429-0200
23.8 Usage Notes
23.8.1 Note on Resonator
Since all kinds of characteristics of the resonator are closely related to the board design by the
user, use the example of resonator connection in this document for only reference; be sure to use
an resonator that has been sufficiently evaluated by the user. Consult with the resonator
manufacturer about the resonator circuit ratings which vary depending on the stray capacitances of
the resonator and installation circuit. Make sure the voltage applied to the oscillation pins do not
exceed the maximum rating.
23.8.2 Notes on Board Design
When using a crystal resonator, the crystal resonator and its load capacitors should be placed as
close as possible to the EXTAL and XTAL pins. Other signal lines should be routed away from
the oscillation circuit to prevent inductive interference with the correct oscillation as shown in
figure 23.5.
C
L2
Signal A Signal B
C
L1
This LSI
XTAL
EXTAL
Prohibited
Figure 23.5 Note on Board Design of Oscillation Circuit Section
23.8.3 Note on Operation Check
This LSI may oscillate at several kHz of frequency even when a crystal resonator is not connected
to the EXTAL and XTAL pins or an external clock is not input. Use this LSI after confirming that
the LSI operates with appropriate frequency.