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

• US 6,515,548 B2
• Filed: 05/21/2001
• Issued: 02/04/2003
• Est. Priority Date: 05/29/2000
• Status: Expired due to Term

• Current Assignee: Seiko NPC Corporation (Seiko Group)
• Original Assignee: Nippon Precision Circuits, Inc. (Seiko Group)
• Inventors: Takahashi, Masayuki, Matsumoto, Toru
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Glenn, Kimberly E
• Application Number:
  US09/862,429
• Publication Number:
  US 20010048349A1
• Time in Patent Office: 624 Days
• Field of Search: 331/25, 331/44, 331/66, 331/70, 331/176
• US Class Current: 331/25
• CPC Class Codes: H03B 5/04 Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00
• CPC Class Codes: H03L 1/025 and a memory for digitally storing correction values
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop

Abstract

A temperature compensated oscillator has a frequency comparing circuit for comparing a frequency of an oscillating output signal of an oscillator circuit and a frequency of an external reference frequency signal externally inputted, and also has a sequential comparing register for determining each bit of a compensation datum based on this comparison. A digital signal from the sequential comparing register is applied 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 stored as 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.

Claims

1. A temperature compensated oscillator comprising:

a temperature detector for outputting an analog temperature signal according to temperature, an A/D converter for converting the analog temperature signal from said temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the digital signal to analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of said variable capacity element, and an oscillator circuit for generating an oscillating output signal by oscillating a resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal;

said temperature compensated oscillator comprising a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted, a register for sequentially determining a value of each bit of of a digital register output of said register based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

wherein said oscillator circuit performs an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit;

the frequency of said oscillating output signal being changed by sequentially determining the value of each bit of said digital register output based on the comparing results of said frequency comparing circuit every comparing operation;

the frequency of the oscillating output signal of said oscillator circuit and the frequency of said external reference frequency signal being conformed to each other; and

the digital register output outputted from said register at a time when said frequency conforming occurs being written to said memory as said compensating data corresponding to a detecting temperature of said temperature detector every predetermined temperature step in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address,

wherein said temperature step corresponds to a predetermined changing width of the detecting temperature of said temperature detector, and said temperature step is partitioned when the digital address signal outputted from said A/D converter shows the predetermined changing width.

3. A temperature compensated oscillator according to any one of claims 1 or 2, wherein said resonator is a crystal resonator, and said variable capacity element is a varicap diode.

2. A temperature compensated oscillator comprising:

a temperature detector for outputting an analog temperature signal according to temperature, an A/D converter for converting the analog temperature signal from said temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the digital signal to analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of said variable capacity element, and an oscillator circuit for generating an oscillating output signal by oscillating a resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal;

said temperature compensated oscillator comprising a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted, a register for sequentially determining a value of each bit of of a digital register output of said register based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

wherein said oscillator circuit performs an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit;

the frequency of said oscillating output signal being changed by sequentially determining the value of each bit of said digital register output based on the comparing results of said frequency comparing circuit every comparing operation;

the frequency of the oscillating output signal of said oscillator circuit and the frequency of said external reference frequency signal being conformed to each other; and

the digital register output outputted from said register at a time when said frequency conforming occurs being written to said memory as said compensating data corresponding to a detecting temperature of said temperature detector every predetermined temperature step in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address,

wherein said temperature step is narrowly set in a temperature range in which a temperature fluctuation of frequency accuracy of said oscillator becomes large.

4. A manufacturing method of a temperature compensated oscillator comprising:

constructing a temperature compensated oscillator including a temperature detector for outputting an analog temperature signal according to temperature, an A/D converter for converting the analog temperature signal from said temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the memory to an analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of the variable capacity element, an oscillator circuit connected to a resonator and generating an oscillating output signal by performing an oscillating operation according to the resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal, a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted, a register for sequentially determining a value of each bit of a digital register output based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

operating said temperature compensated oscillator at a predetermined specific temperature;

inputting said external reference frequency signal to said frequency comparing circuit;

conforming frequency by adjusting said oscillator circuit to perform an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit, and changing the frequency of said oscillating output signal by sequentially determining the value of each bit of said digital register output based on comparing results of said frequency comparing circuit every comparing operation, to conform the frequency of the oscillating output signal of said oscillator circuit to the frequency of said external reference frequency signal;

writing the digital register output outputted from said register, at a time when said frequency of the oscillating output signal and the frequency of said external reference signal conform, to said memory as said compensating data corresponding to a detecting temperature of said temperature detector in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address; and

performing said writing of said compensating data within a predetermined temperature compensating range to said memory by changing a circumferential temperature of said temperature compensated oscillator at a predetermined speed from said specific temperature so as to cross said predetermined temperature compensating range, and performing said writing operation of said compensating data at each occurrence of said predetermined temperature step,

wherein said predetermined temperature step corresponds to a predetermined changing width of the detecting temperature of said temperature detector, and said temperature step is partitioned when the digital signal outputted from said A/D converter shows the predetermined changing width.

6. A manufacturing method of a temperature compensated oscillator according to claims 4 or 5, wherein said resonator is a crystal resonator, and said variable capacity element is a varicap diode.

5. A manufacturing method of a temperature compensated oscillator comprising:

constructing a temperature compensated oscillator including a temperature detector for outputting an analog temperature signal according to temperature, an A/D converter for converting the analog temperature signal from said temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the memory to an analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of the variable capacity element, an oscillator circuit connected to a resonator and generating an oscillating output signal by performing an oscillating operation according to the resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal, a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted, a register for sequentially determining a value of each bit of a digital register output based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

operating said temperature compensated oscillator at a predetermined specific temperature;

inputting said external reference frequency signal to said frequency comparing circuit;

conforming frequency by adjusting said oscillator circuit to perform an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit, and changing the frequency of said oscillating output signal by sequentially determining the value of each bit of said digital register output based on comparing results of said frequency comparing circuit every comparing operation, to conform the frequency of the oscillating output signal of said oscillator circuit to the frequency of said external reference frequency signal;

writing the digital register output outputted from said register, at a time when said frequency of the oscillating output signal and the frequency of said external reference signal conform, to said memory as said compensating data corresponding to a detecting temperature of said temperature detector in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address; and

performing said writing of said compensating data within a predetermined temperature compensating range to said memory by changing a circumferential temperature of said temperature compensated oscillator at a predetermined speed from said specific temperature so as to cross said predetermined temperature compensating range, and performing said writing operation of said compensating data at each occurrence of said predetermined temperature step,

wherein said temperature step is narrowly set in a temperature range in which a temperature fluctuation of frequency accuracy of said oscillator becomes large.

7. A manufacturing method of a temperature compensated oscillator comprising:

constructing a temperature compensated oscillator including a temperature detector for outputting an analog temperature signal according to temperature, an A/D converter for converting the analog temperature signal from said temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the memory to an analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of the variable capacity element, an oscillator circuit connected to a resonator and generating an oscillating output signal by performing an oscillating operation according to the resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal, a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted, a register for sequentially determining a value of each bit of a digital register output based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

operating said temperature compensated oscillator at a predetermined specific temperature;

inputting said external reference frequency signal to said frequency comparing circuit;

conforming frequency by adjusting said oscillator circuit to perform an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit, and changing the frequency of said oscillating output signal by sequentially determining the value of each bit of said digital register output based on comparing results of said frequency comparing circuit every comparing operation, to conform the frequency of the oscillating output signal of said oscillator circuit to the frequency of said external reference frequency signal;

writing the digital register output outputted from said register, at a time when said frequency of the oscillating output signal and the frequency of said external reference signal conform, to said memory as said compensating data corresponding to a detecting temperature of said temperature detector in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address; and

performing said writing of said compensating data within a predetermined temperature compensating range to said memory by changing a circumferential temperature of said temperature compensated oscillator at a predetermined speed from said specific temperature so as to cross said predetermined temperature compensating range, and performing said writing operation of said compensating data at each occurrence of said predetermined temperature step,

wherein said specific temperature lies outside said predetermined temperature range.

8. An integrated circuit for a temperature compensated oscillator comprising:

an A/D converter for converting an analog temperature signal from a temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the digital signal to analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of said variable capacity element, an oscillator circuit for externally connecting to a resonator and generating an oscillating output signal by oscillating the resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal, a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted,a register for sequentially determining a value of each bit of of a digital register output of said register based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

wherein said oscillator circuit performs an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit;

the frequency of said oscillating output signal being changed by sequentially determining the value of each bit of said digital register output based on the comparing results of said frequency comparing circuit every comparing operation;

the frequency of the oscillating output signal of said oscillator circuit and the frequency of said external reference frequency signal being conformed to each other; and

the digital register output outputted from said register at a time when said frequency conforming occurs being written to said memory as said compensating data corresponding to a detecting temperature of said temperature detector every predetermined temperature step in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address,

wherein said temperature step corresponds to a predetermined changing width of the detecting temperature of said temperature detector, and said temperature step is partitioned when the digital address signal outputted from said A/D converter shows the predetermined changing width.

10. An integrated circuit for temperature compensated oscillation according to claims 8 or 9, wherein said resonator is a crystal resonator, and said variable capacity element is a varicap diode.

9. An integrated circuit for a temperature compensated oscillation comprising:

an A/D converter for converting an analog temperature signal from a temperature detector to a digital address signal, a memory from which compensating data are read using the digital address signal from said A/D converter as an address, a D/A converter for converting said compensating data from the digital signal to analog compensating signal, a variable capacity element being sent the analog compensating signal from said D/A converter as a control voltage of said variable capacity element, an oscillator circuit for externally connecting to a resonator and generating an oscillating output signal by oscillating the resonator using said variable capacity element as a frequency adjusting element of said oscillating output signal, a frequency comparing circuit for comparing frequencies of said oscillating output signal and an external reference frequency signal externally inputted,a register for sequentially determining a value of each bit of of a digital register output of said register based on frequency comparing results of said frequency comparing circuit, and a switching circuit for selectively supplying the compensating data read from said memory and the digital register output outputted from said register to said D/A converter;

wherein said oscillator circuit performs an oscillating operation by supplying the digital register output outputted from said register to said D/A converter through said switching circuit;

the frequency of said oscillating output signal being changed by sequentially determining the value of each bit of said digital register output based on the comparing results of said frequency comparing circuit every comparing operation;

the frequency of the oscillating output signal of said oscillator circuit and the frequency of said external reference frequency signal being conformed to each other; and

the digital register output outputted from said register at a time when said frequency conforming occurs being written to said memory as said compensating data corresponding to a detecting temperature of said temperature detector every predetermined temperature step in a state in which the digital address signal outputted from said A/D converter in accordance with said detecting temperature at that time is set as an address,

wherein said temperature step is narrowly set in a temperature range in which a temperature fluctuation of frequency accuracy of said oscillator becomes large.