CHAPTER 6 CLOCK GENERATOR
Page 118 of 920
Figure 6 - 15 Example of External Circuit of XT1 Oscillator
Caution 1. When using the X1 oscillator and XT1 oscillator, wire as follows in the area enclosed by the broken lines in the
Figures 6 - 14 and 6 - 15 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.
The XT1 oscillator is a circuit with low amplification in order to achieve low-power consumption. Note the
following points when designing the circuit.
• Pins and circuit boards include parasitic capacitance. Therefore, perform oscillation evaluation using a circuit
board to be actually used and confirm that there are no problems.
• When using the ultra-low power consumption oscillation (AMPHS1, AMPHS0 = 1, 0) as the mode of the XT1
oscillator, evaluate the resonators.
• Make the wiring between the XT1 and XT2 pins and the resonators as short as possible, and minimize the
parasitic capacitance and wiring resistance. Note this particularly when the ultra-low power consumption
oscillation (AMPHS1, AMPHS0 = 1, 0) is selected.
• Configure the circuit of the circuit board, using material with little wiring resistance.
• Place a ground pattern that has the same potential as V
SS
as much as possible near the XT1 oscillator.
• Be sure that the signal lines between the XT1 and XT2 pins, and the resonators do not cross with the other
signal lines. Do not route the wiring near a signal line through which a high fluctuating current flows.
• The impedance between the XT1 and XT2 pins may drop and oscillation may be disturbed due to moisture
absorption of the circuit board in a high-humidity environment or dew condensation on the board. When using
the circuit board in such an environment, take measures to damp-proof the circuit board, such as by coating.
• When coating the circuit board, use material that does not cause capacitance or leakage between the XT1 and
XT2 pins.
(a) Crystal oscillation
(b) External clock
32.768
kHz
EXCLKS
External clock
XT2
XT1
V
SS
Содержание RL78/G1H
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