SH7144 Datasheet, PDF (89/773 Pages) Renesas Technology Corp – Hitachi SuperH RISC engine

C_L1
EXTAL
XTAL
R_d
C_L2
C_L1 = C_L2 = 18–22 pF (Recommended value)
Figure 4.2 Connection of the Crystal Oscillator (Example)
Table 4.2 Damping Resistance Values
Frequency (MHz)
4
8
10
12.5
Rd (Ω)
500
200
0
0
Crystal Resonator: Figure 4.3 shows an equivalent circuit of the crystal resonator. Use a crystal
resonator with the characteristics listed in table 4.3.
XTAL
C_L
L
Rs
EXTAL
C₀
Figure 4.3 Crystal Resonator Equivalent Circuit
Table 4.3 Crystal Resonator Characteristics
Frequency (MHz)
4
8
10
12.5
Rs max (Ω)
120
80
60
50
C0 max (pF)
7
7
7
7
4.1.2 External Clock Input Method
Figure 4.4 shows an example of an external clock input connection. In this case, make the external
clock high level to stop it when in software standby mode. During operation, make the external
input clock frequency 4 to 12.5 MHz.
When leaving the XTAL pin open, make sure the parasitic capacitance is less than 10 pF.
Even when inputting an external clock, be sure to wait at least the oscillation stabilization time in
power-on sequence or in releasing software standby mode, in order to ensure the PLL stabilization
time.
Rev. 2.0, 09/02, page 49 of 732