| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the accuracy of an oscillation frequency by absorbing dispersion of a circuit constant in production. SOLUTION: A capacitor 23 performs charging/discharging through a resistor 22 corresponding to the comparing output of a comparator circuit 20. The comparing output of the comparator circuit 20 becomes a low level until increasing the terminal voltage of the capacitor 23 to a first reference voltage V1 and becomes high level until lowering the terminal voltage to a second reference voltage V2. A reference voltage generating part 13 has first and second voltage divider circuits 14 and 15 for generating the first reference voltage V1 and the second reference voltage V2 at the interval of plural stages, a first selector circuit 17 for outputting the reference voltage selected by a select signal from an EEPROM 19 out of the first reference voltages V1 of plural stages and a second selector circuit 18 for outputting the reference voltage selected by the select signal out of the second reference voltages V2 of plural stages. The selected reference voltages V1 and V2 are inputted to the comparator circuit 20 by any one of first and second switching circuits 24 and 25.</p> |
