Temperature compensation type oscillator

Abstract

A temperature compensated oscillator includes an oscillation circuit ( 20 ), a temperature detection circuit ( 18 ), and a temperature compensation circuit ( 30 ) for keeping the frequency of the output signal of the oscillation circuit ( 20 ) substantially constant based on the temperature detection signal from the temperature detection circuit, in which a selection circuit ( 40 ) is provided which selects to enable or disable a temperature compensation function of the temperature compensation circuit ( 30 ). Accordingly, in a state in which a quartz crystal, an IC chip, and so on are mounted in a package, the temperature compensation function of the temperature compensation circuit ( 30 ) is disabled, the oscillation circuit ( 20 ) is operated to accurately adjust the temperature characteristics of the quartz crystal itself, and thereafter operation of creating compensation data and storing it into a memory can be subsequently performed.

1 . A temperature compensated oscillator, comprising: 
 an oscillation circuit whose oscillation frequency varies with a temperature change;    an output line for outputting a signal based on an oscillation output of said oscillation circuit;    a temperature detection circuit for detecting a temperature state near said oscillation circuit; and    a temperature compensation circuit for keeping a frequency of the signal outputted to said output line substantially constant based on an output from said temperature detection circuit,    wherein a selection means is provided which selects whether to enable or disable a temperature compensation function of said temperature compensation circuit.    
   
   
       2 . The temperature compensated oscillator according to  claim 1 , further comprising: 
 a variable frequency division circuit between said oscillation circuit and said output line,    wherein said selection means has means for allowing said temperature compensation circuit to vary a frequency division ratio of said variable frequency division circuit depending on a temperature detected by said temperature detection circuit when enabling the temperature compensation function of said temperature compensation circuit, and fixing the frequency division ratio of said variable frequency division circuit to a predetermined value when disabling the temperature compensation fiction.    
   
   
       3 . The temperature compensated oscillator according to  claim 1   wherein said oscillation circuit has an oscillation capacitor, and    wherein said selection means has means for allowing said temperature compensation circuit to vary a capacitance value of said oscillation capacitor depending on a temperature detected by said temperature detection circuit when enabling the temperature compensation function of said temperature compensation circuit, and fixing the capacitance value of said oscillation capacitor to a predetermined capacitance value when disabling the temperature compensation function.    
   
   
       4 . The temperature compensated oscillator according to  claim 3 , 
 wherein said oscillation capacitor includes a variable capacitor which varies in capacitance value in accordance with a voltage applied thereto, and said temperature compensation circuit has means for changing the voltage applied to the variable capacitor to change the capacitance value of said oscillation capacitor.    
   
   
       5 . The temperature compensated oscillator according to  claim 3 , 
 wherein said oscillation capacitor includes a plurality of fixed capacitors, and said temperature compensation circuit has means for changing connection states of the plurality of fixed capacitors to change the capacitance value of said oscillation capacitor.    
   
   
       6 . The temperature compensated oscillator according to  claim 4 , 
 wherein said selection means has means for fixing the voltage applied to the variable capacitor to a predetermined value when fixing the capacitance value of said oscillation capacitor to the predetermined capacitance value.    
   
   
       7 . The temperature compensated oscillator according to  claim 4 , 
 wherein said selection means has means for separating the variable capacitor so that the variable capacitor is not included in said oscillation capacitor when fixing the capacitance value of said oscillation capacitor to the predetermined capacitance value.    
   
   
       8 . The temperature compensated oscillator according to  claim 1 , further comprising: 
 a selection information storage circuit which stores control information for controlling a selection state of said selection means.    
   
   
       9 . The temperature compensated oscillator according to  claim 1 , further comprising: 
 a compensation data storage circuit which stores temperature compensation data of said temperature compensation circuit.    
   
   
       10 . The temperature compensated oscillator according to  claim 1 , further comprising: 
 a selection information storage circuit which stores control information for controlling a selection state of said selection means; and    a compensation data storage circuit which stores temperature compensation data of said temperature compensation circuit,    wherein said selection information storage circuit and said compensation data storage circuit form an integrated storage circuit.    
   
   
       11 . The temperature compensated oscillator according to  claim 1 , further comprising: 
 a control information input terminal for inputting from outside control information for controlling a selection state of said selection means.    
   
   
       12 . The temperature compensated oscillator according to  claim 11 , 
 wherein said control information input terminal is an external terminal provided on a package constituting said temperature compensated oscillator.    
   
   
       13 . The temperature compensated oscillator according to  claim 8 , 
 wherein said selection information storage circuit is composed of a predetermined conductive pattern and stores information for controlling a selection state of said selection means caused by the conductive pattern being cut.