SH7080_09 Datasheet, PDF (145/1622 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family

Section 4 Clock Pulse Generator (CPG)
4.8 Usage Notes
4.8.1 Note on Crystal Resonator
A sufficient evaluation at the user’s site is necessary to use the LSI, by referring the resonator
connection examples shown in this section, because various characteristics related to the crystal
resonator are closely linked to the user’s board design. As the oscillator circuit's circuit constant
will depend on the resonator and the floating capacitance of the mounting circuit, the value of each
external circuit’s component should be determined in consultation with the resonator
manufacturer. The design must ensure that a voltage exceeding the maximum rating is not applied
to the oscillator pin.
4.8.2 Notes on Board Design
Measures against radiation noise are taken in this LSI. If further reduction in radiation noise is
needed, it is recommended to use a multiple layer board and provide a layer exclusive to the
system ground.
When using a crystal resonator, place the crystal resonator and its load capacitors as close as
possible to the XTAL and EXTAL pins. Do not route any signal lines near the oscillator circuitry
as shown in figure 4.5. Otherwise, correct oscillation can be interfered by induction.
Avoid
C_L2
Signal A Signal B
This LSI
XTAL
EXTAL
C_L1
Figure 4.5 Cautions for Oscillator Circuit Board Design
Rev. 4.00 Dec. 15, 2009 Page 85 of 1558
REJ09B0181-0400