Renesas RL78 Series User Manual page 140

RL78/G1D
Cautions 7. The XT1 oscillator is a circuit with low amplification in order to achieve low-power
Remark f
R01UH0515EJ0120 Rev.1.20
Dec 16, 2016
consumption. Note the following points when designing the circuit.
● Pins and circuit boards include parasitic capacitance.
oscillation evaluation using a circuit board to be actually used and confirm that
there are no problems.
● Before using the ultra-low power consumption oscillation (AMPHS1, AMPHS0 = 1,
0) as the mode of the XT1 oscillator, evaluate the resonators described in 6.7
Resonator and Oscillator Constants.
● 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
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.
: X1 clock frequency
X
CHAPTER 6 CLOCK GENERATOR
Therefore, perform
as much as possible
SS
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