Renesas RL78/G1H

RL78/G1H CHAPTER 6 CLOCK GENERATOR
R01UH0575EJ0120 Rev. 1.20 Page 103 of 920
Dec 22, 2016
Caution 7. 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 parasitic capacitance and 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.
Remark
fX: X1 clock frequency