Note On Oscillators; Figure 4.10 Example Of Crystal And Ceramic Oscillator Element Arrangement - Renesas H8/3847R Series Hardware Manual

8-bit single-chip microcomputer super low power

Table of Contents

Section 4 Clock Pulse Generators

Note on Oscillators

Oscillator characteristics are closely related to board design and should be carefully evaluated by

the user in mask ROM, ZTAT™ and F-ZTAT™ versions, referring to the examples shown in this

section. Oscillator circuit constants will differ depending on the oscillator element, stray

capacitance in its interconnecting circuit, and other factors. Suitable constants should be

determined in consultation with the oscillator element manufacturer. Design the circuit so that the

oscillator element never receives voltages exceeding its maximum rating.

Figure 4.11 (1) shows an example measuring circuit with the negative resistance suggested by the

oscillator manufacturer. Note that if the negative resistance of the circuit is less than that suggested

by the oscillator manufacturer, it may be difficult to start the main oscillator.

If it is determined that oscillation is not occurring because the negative resistance is lower than the

level suggested by the oscillator manufacturer, the circuit may be modified as shown in figure 4.11

(2) through (4). Which of the modification suggestions to use and the capacitor capacitance should

be decided based upon an evaluation of factors such as the negative resistance and the frequency

Rev. 6.00 Aug 04, 2006 page 126 of 680

REJ09B0145-0600