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20.6
Usage Notes
20.6.1
Note on Crystal Resonator
As various characteristics related to the crystal resonator are closely linked to the user's board
design, thorough evaluation is necessary on the user's part, using the resonator connection
examples shown in this section as a guide. As the resonator circuit ratings will depend on the
floating capacitance of the resonator and the mounting circuit, the ratings should be determined in
consultation with the resonator manufacturer. The design must ensure that a voltage exceeding the
maximum rating is not applied to the oscillator pin.
20.6.2
Note on Board Design
When designing the board, place the crystal resonator and its load capacitors as close as possible
to the XTAL and EXTAL pins. Other signal lines should be routed away from the oscillator
circuit, as shown in figure 20.6. This is to prevent induction from interfering with correct
oscillation.
Figure 20.6 Note on Board Design of Oscillator Circuit
Figure 20.7 shows external circuitry recommended to be provided around the PLL circuit. Place
oscillation settling capacitor C1 and resistor R1 close to the PLLCAP pin, and ensure that no other
signal lines cross this line. Separate PLLVss from the other Vcc and Vss lines at the board power
supply source, and be sure to insert bypass capacitors CB close to the pins.
Rev. 1.0, 09/02, page 474 of 568
Avoid
Signal A Signal B
C
L2
C
L1
This LSI
XTAL
EXTAL
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