D12320VF25IV Datasheet, PDF (947/1304 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 20 Clock Pulse Generator
Crystal Resonator: Figure 20.3 shows the equivalent circuit of the crystal resonator. Use a crystal
resonator that has the characteristics shown in table 20.3 and the same resonance frequency as the
system clock (φ).
XTAL
C_L
L
R_s
EXTAL
C₀
AT-cut parallel-resonance type
Figure 20.3 Crystal Resonator Equivalent Circuit
Table 20.3 Crystal Resonator Characteristics
Frequency (MHz)
RS max (Ω)
C0 max (pF)
2
4
8
12
16
20
25
500
120
80
60
50
40
40
7
7
7
7
7
7
7
Notes on Board Design: When a crystal resonator is connected, the following points should be
noted:
Other signal lines should be routed away from the oscillator circuit to prevent induction from
interfering with correct oscillation. See figure 20.4.
When designing the board, place the crystal resonator and its load capacitors as close as possible
to the XTAL and EXTAL pins.
Avoid
C_L2
Signal A Signal B
Chip
XTAL
EXTAL
C_L1
Figure 20.4 Example of Incorrect Board Design
Rev.6.00 Sep. 27, 2007 Page 915 of 1268
REJ09B0220-0600