Methods and apparatus to control frequency offsets in digitally controlled crystal oscillators

• US 20050093638A1
• Filed: 10/15/2004
• Published: 05/05/2005
• Est. Priority Date: 11/03/2003
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Lin, Heng-Chih, Leipold, Dirk, Chen, Chien-Chung
• Application Number:
  US10/966,220
• Publication Number:
  US 20050093638A1
• Time in Patent Office: Days
• US Class Current: 331/176
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 1/028 of generators comprising piezoelectric resonators H03L1/021, H03L1/022 take precedence; oscillation generators with a piezoelectric resonator H03B5/32
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation

Abstract

Methods and systems of adjusting an oscillator frequency are disclosed. One example method includes reading a temperature associated with an oscillator, reading a first tuning code associated with the temperature from a memory, and tuning the oscillator with the first tuning code. The example method may further include determining a second tuning code, and storing the second tuning code and an indication of the temperature in the memory.

Claims

1. A method of adjusting an oscillator frequency, comprising:

reading a temperature associated with an oscillator;

reading a first tuning code associated with the temperature from a memory;

tuning the oscillator with the first tuning code;

determining a second tuning code; and

storing the second tuning code and an indication of the temperature in the memory.

2. A method as defined by claim 1, further comprising tuning the oscillator with the second tuning code.

3. A method as defined by claim 1, wherein tuning the oscillator with the first tuning code comprises changing a reactive load on the oscillator.

4. A method as defined by claim 1, wherein the temperature is a first temperature, and further comprising reading a second temperature associated with the oscillator and storing the second temperature is association with the second tuning code in the memory.

5. A method as defined by claim 1, wherein determining the second tuning code comprises:

receiving a frequency indication; and

determining the second tuning code based on the frequency indication.

6. A method as defined by claim 5, further comprising establishing communication with another entity and receiving the frequency indication therefrom.

7. A method as defined by claim 1, further comprising reading the second tuning code from the memory and tuning the oscillator with the second tuning code.

8. A method as defined by claim 1, wherein storing the second tuning code and the indication of the temperature in the memory comprises storing the second tuning code and the indication of the temperature in a lookup table including a plurality of temperatures and a plurality of corresponding tuning codes.

9. A frequency control system comprising:

an oscillator;

an adjustable reactive load coupled to the oscillator;

a temperature sensor adapted to sense a temperature associated with the oscillator;

a memory; and

a controller coupled to the adjustable reactive load, the temperature sensor, and the memory, the controller configured to;

read a temperature associated with the oscillator;

read a first tuning code associated with the temperature from the memory;

tune the oscillator with the first tuning code;

determine a second tuning code; and

store the second tuning code and an indication of the temperature in the memory.

10. A system defined by claim 9, wherein the oscillator comprises one of a crystal oscillator and a resonator.

11. A system defined by claim 9, wherein the memory comprises non-volatile memory.

12. A system defined by claim 9, further comprising a receiver coupled to the controller and configured to provide the controller with a frequency indication.

13. A system defined by claim 12, wherein the frequency indication comprises a frequency control burst.

14. A system defined by claim 12, wherein the controller is configured to determine the second tuning code based on the frequency indication.

15. A system defined by claim 9, wherein the memory stores a lookup table including a plurality of temperatures and a plurality of corresponding tuning codes.

16. A machine-accessible medium having a plurality of machine accessible instructions that, when executed, cause a machine to:

read a temperature associated with an oscillator;

read a first tuning code associated with the temperature from a memory;

tune the oscillator with the first tuning code;

determine a second tuning code; and

store the second tuning code and an indication of the temperature in the memory.

17. A machine-accessible medium as defined by claim 16, further comprising instructions that, when executed, cause the machine to tune the oscillator with the second tuning code.

18. A machine-accessible medium as defined by claim 16, wherein the memory comprises flash memory.

19. A machine-accessible medium as defined by claim 18, wherein the memory comprises a lookup table including a plurality of temperatures and a plurality of tuning codes.

20. A machine-accessible medium as defined by claim 16, further comprising instructions that, when executed, cause the machine to:

receive a frequency indication; and

determine the second tuning code based on the frequency indication.

21. A controller for adjusting an oscillator frequency comprising:

a memory;

a sensor interface to receive a temperature value;

an initial DCXO code setter to access the memory to retrieve a first DCXO code based on the temperature value; and

a DCXO code adjuster to generate a second DCXO code based on frequency data received from an external device, and to store the second DCXO code in the memory.

22. A controller as defined by claim 21, wherein the DCXO code adjuster tunes an oscillator by outputting the first DCXO code to a reactive load coupled to the oscillator.

23. A controller as defined by claim 21, wherein the memory comprises a lookup table including a plurality of temperatures and a plurality of corresponding tuning codes.