HD64F38602R Datasheet, PDF (105/552 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 4 Clock Pulse Generators
Figure 4.10 (1) shows an example measuring circuit with the negative resistance recommended by
the resonator manufacturer. Note that if the negative resistance of the circuit is less than that
recommended by the resonator manufacturer, it may be difficult to start the main oscillator.
If it is determined that oscillation does not occur because the negative resistance is lower than the
level recommended by the resonator manufacturer, the circuit must be modified as shown in figure
4.10 (2) through (4). Which of the modification suggestions to use and the capacitor capacitance
should be decided based upon evaluation results such as the negative resistance and the frequency
deviation.
Modification
point
OSC1
C1
OSC1
C1
OSC2
C2
Negative resistance,
addition of -R
(1) Negative Resistance Measuring Circuit
Modification
point
C1
OSC1
OSC2
C2
(2) Oscillator Circuit Modification Suggestion 1
Modification
point
C3
C1
OSC1
C2
OSC2
OSC2
C2
(3) Oscillator Circuit Modification Suggestion 2
(4) Oscillator Circuit Modification Suggestion 3
Figure 4.10 Negative Resistance Measurement and Circuit Modification Suggestions
Rev. 3.00 May 15, 2007 Page 73 of 518
REJ09B0152-0300