Datasheet

CHAPTER 5 CLOCK GENERATOR
User’s Manual U18698EJ1V0UD
120
5.4 System Clock Oscillator
5.4.1 X1 oscillator
The X1 oscillator oscillates with a crystal resonator or ceramic resonator (2 to 10 MHz) connected to the X1 and X2
pins.
An external clock can also be input. In this case, input the clock signal to the EXCLK pin.
Figure 5-10 shows an example of the external circuit of the X1 oscillator.
Figure 5-10. Example of External Circuit of X1 Oscillator
(a) Crystal or ceramic oscillation (b) External clock
VSS
X1
X2
Crystal resonator
or
ceramic resonator
EXCLK
External clock
5.4.2 XT1 oscillator
The XT1 oscillator oscillates with a crystal resonator (standard: 32.768 kHz) connected to the XT1 and XT2 pins.
Figure 5-11 shows an example of the external circuit of the XT1 oscillator.
Figure 5-11. Example of External Circuit of XT1 Oscillator
(a) Crystal oscillation
XT2
V
SS
XT1
32.768
kHz
Caution 1. When using the X1 oscillator and XT1 oscillator, wire as follows in the area enclosed by the
broken lines in the Figures 5-10 and 5-11 to avoid an adverse effect from wiring capacitance.
• Keep the wiring length as short as possible.
• Do not cross the wiring with the other signal lines. Do not route the wiring near a signal
line through which a high fluctuating current flows.
• Always make the ground point of the oscillator capacitor the same potential as V
SS. Do
not ground the capacitor to a ground pattern through which a high current flows.
• Do not fetch signals from the oscillator.
Note that the XT1 oscillator is designed as a low-amplitude circuit for reducing power
consumption.