GENERATING CIRCUIT OF CRYSTAL REFERENCE SIGNAL

PURPOSE:To ensure the highly accurate compensation of temperature in terms of a circuit by using a code inverter which delivers the control voltage for control of the dividing ratio of a frequency dividing circuit with the output of an A/D converter used as an input. CONSTITUTION:The output of a temperature sensor, e.g., a thermistor 1 provided in a temperature atmosphere approximately equal to a crystal oscillator 6 delivers the analog voltage proportional to the temperature of said atmosphere and then supplies it to an A/D converter 2. The converter 2 converts the temperature analog quantity into the digital value with appropriate resolution, and this output line of several bits is supplied to a code converter 3 consisting of an ROM, for example. The digital value corresponding to the temperature is converted by the converter 3 into the set value of dividing ratio of a programmable frequency dividing circuit 4 and then delivered. If the dividing ratio is set so that the frequency of an output 7 of the circuit 4 is set constant, the output 7 can deliver a reference signal of a stable frequency over a range of all temperatures.