Patent ID: 6788159
Filing Date: 2004-09-07
Classification: H03J,H03L

Abstract:
A temperature compensated oscillator, comprising:a temperature detector that outputs an analog signal depending on a temperature; an A/D converter for converting the analog signal from said temperature detector into a digital signal; a memory from which compensation data is read out using the digital signal from said A/D converter as an address; a capacitor array for selectively connecting a plurality of capacitive elements to an oscillation circuit based on said compensation data; said oscillation circuit causing a resonator such as a crystal resonator to oscillate thereby generating an oscillation output signal, and using said capacitor array as a frequency adjusting element for said oscillation output signal; a frequency comparison circuit for comparing frequencies of an external reference frequency signal and said oscillation output signal; a register in which a value of each bit is sequentially determined based on the frequency comparison result from said frequency comparison circuit; a switching circuit for selectively supplying the compensation data read out from the memory and a digital signal output from said register to said capacitor array; a voltage variable capacitive element connected to said capacitor array; a control voltage generation circuit for generating control voltage to control the capacitance of said voltage variable capacitive element in response to the analog signal from said temperature detector; said register supplying a digital signal output to said capacitor array through said switching circuit and said plurality of capacitive elements being connected to said oscillation circuit in response to said digital signal, so that said oscillation circuit carries out oscillation operation; and said register having the value of each bit sequentially determined based on the comparison result for each comparison operation by said frequency comparison circuit to change the frequency of said oscillation output signal, the digital signal output from said register when the frequency of said oscillation output signal of said oscillation circuit is matched with a particular frequency being written by a writing operation in said memory as said compensation data corresponding to a temperature that can be addressed using a digital signal output from said A/D converter corresponding to the temperature detected by said temperature detector at the time, so that the writing operation is carried out for each temperature step.