6.2
Oscillator Circuit
6.2.1
Oscillator (Generic Device)
If an external crystal is connected across the EXTAL and XTAL pins, the on-chip oscillator circuit
generates a system clock signal. Alternatively, an external clock signal can be applied to the
EXTAL pin.
Connecting an External Crystal
Circuit Configuration: An external crystal can be connected as in the example in figure 6.2.
Table 6.1 indicates the appropriate damping resistance Rd. An AT-cut parallel resonance crystal
should be used.
CL1
EXTAL
XTAL
Rd
CL1 = C L2 = 10 pF to 22 pF
CL2
Figure 6.2 Connection of Crystal Oscillator (Example)
Table 6.1 Damping Resistance
Frequency (MHz)
2
4
8
10
0
12
0
16
0
Rd max (Ω)
1 k
500
200
Crystal Oscillator: Figure 6.3 shows an equivalent circuit of the crystal resonator. The crystal
resonator should have the characteristics listed in table 6.2.
97
RENESAS [ RENESAS TECHNOLOGY CORP ]
