Temperature compensated oscillator, its manufacturing method, and integrated circuit for temperature compensated oscillator

摘要

An object of the invention is to provide a temperature compensated oscillator and reduce manufacture cost of this oscillator. Therefore, the temperature compensated oscillator has a frequency comparing circuit for comparing the frequency of an oscillating output signal of an oscillator circuit and the frequency of an external reference frequency signal externally inputted, and also has a sequential comparing register for determining each bit on the basis of results of this comparison. A digital signal from the sequential comparing register is set to an input of a D/A converter for generating a control voltage of a varicap diode. The temperature compensated oscillator performs a self compensating operation for sequentially determining each bit of the sequential comparing register every frequency comparison, and conforming the frequency of the oscillating output signal to that of the external reference frequency signal. The digital signal from the sequential comparing register is set to compensating data corresponding to a detecting temperature of a temperature detector at that time. The compensating data are determined by performing the self compensating operation every predetermined temperature change detected by the temperature detector.