OSCILLATORS HAVING ARBITRARY FREQUENCIES AND RELATED SYSTEMS AND METHODS

• US 20120163134A1
• Filed: 03/02/2012
• Published: 06/28/2012
• Est. Priority Date: 12/23/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand9, Inc.
• Inventors: Schoepf, Klaus Juergen, Rebel, Reimund, Kuypers, Jan H.
• Granted Patent: US 8,896,385 B2
• Time in Patent Office: Days
• US Class Current: 368/200
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H03L 7/16 Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop

Abstract

Systems and methods for operating with oscillators configured to produce an oscillating signal having an arbitrary frequency are described. The frequency of the oscillating signal may be shifted to remove its arbitrary nature by application of multiple tuning signals or values to the oscillator. Alternatively, the arbitrary frequency may be accommodated by adjusting operation one or more components of a circuit receiving the oscillating signal.

Claims

1. A circuit, comprising:

a reference clock comprising;

a reference oscillator configured to produce a reference oscillator signal having an arbitrary frequency that is not a power of 2; and

counter circuitry configured to receive the reference oscillator signal and count a number of oscillations of the reference oscillator signal,

wherein the reference clock is configured to output a reference clock signal with a time base based on the number of oscillations of the reference oscillator signal counted by the counter circuitry; and

a real time clock coupled to the reference clock and configured to receive the reference clock signal having the time base, and configured to produce an output indicative of current time.

2. The circuit of claim 1, wherein the time base is one second.

3. The circuit of claim 1, wherein the real time clock does not include a divider configured to operate on the reference clock signal.

4. The circuit of claim 1, wherein the reference clock further comprises comparator circuitry configured to compare the number of oscillations of the reference oscillator signal as counted by the counter circuitry to a reference number.

5. The circuit of claim 4, wherein the comparator circuitry is configured to produce a comparator output exhibiting a state change when the number of oscillations of the reference oscillator signal equals or exceeds the reference number.

6. The circuit of claim 5, further comprising a feedback loop between an output of the counter circuitry and a reset port of the counter circuitry.

7. The circuit of claim 6, further comprising a pulse generator coupled to an output of the comparator circuitry to receive the comparator output and configured to produce the reference clock signal.

8. The circuit of claim 5, wherein the reference number is a frequency of the reference oscillator.

9. The circuit of claim 5, wherein the reference number is stored in memory.

10. The circuit of claim 9, wherein the memory is in the reference oscillator.

11. The circuit of claim 5, wherein the reference clock is further configured to determine an accumulated error and to adjust an output of the comparator circuitry based on the accumulated error.

12. The circuit of claim 11, further comprising temperature compensation circuitry configured to compensate the accumulated error or the comparator output based on a measured temperature.

13. The circuit of claim 5, wherein the reference oscillator is frequency tunable, wherein the counter circuitry is an integer counter, and wherein the circuit further comprising tuning circuitry configured to tune a frequency of the reference oscillator to an integer value.

14. The circuit of claim 1, further comprising temperature compensation circuitry configured to generate a tuning signal to tune the arbitrary frequency of the reference oscillator in response to temperature induced variations in the arbitrary frequency.

15. A circuit comprising:

a tunable reference oscillator configured to produce a tunable reference oscillating signal; and

a real time clock configured to receive a reference clock signal derived from the tunable reference oscillating signal and produce an output indicative of current time.

16. The circuit of claim 15, wherein the tunable reference oscillator comprises memory storing an indication of a frequency of operation of the tunable reference oscillator.

17. The circuit of claim 15, wherein the tunable reference oscillator is tuned to an arbitrary frequency N Hz, wherein N is an integer.

18. The circuit of claim 17, further comprising a counter configured to count oscillations of the reference oscillating signal and to produce a clock pulse after N oscillations.

19. The circuit of claim 17, further comprising a counter configured to count oscillations of the reference oscillating signal and to produce a clock pulse after N/2^x oscillations, where x is an integer.

20. The circuit of claim 15, further comprising circuitry configured to frequency tune the tunable reference oscillator in response to temperature variations.

21. The circuit of claim 20, further comprising a counter and circuitry for comparing an output of the counter to a reference value, and wherein the circuitry configured to frequency tune the tunable reference oscillator does so without altering the counter or the reference value.

22. The circuit of claim 15, further comprising a counter and circuitry for comparing an output of the counter to a reference value, and wherein the circuit is configured to account for temperature drift of the tunable reference oscillator by changing the counter or the reference value.

23. The circuit of claim 22, wherein the circuit is configured to account for temperature drift of the tunable reference oscillator by changing the counter or the reference value and by frequency tuning the tunable reference oscillator.

24. A method of operating clock circuitry, comprising:

generating a reference oscillating signal having an arbitrary frequency that is not a power of 2;

counting a number of oscillations of the reference oscillating signal;

producing a reference clock signal based on the number of oscillations of the reference oscillating signal counted;

providing the reference clock signal to a real time clock; and

generating an output of the real time clock indicative of current time.

25. The method of claim 24, wherein generating the reference oscillating signal comprises using an arbitrary frequency reference oscillator, and wherein the method further comprises frequency tuning the arbitrary frequency reference oscillator in response to temperature variations.

26. The method of claim 24, wherein producing the reference clock signal comprises comparing the number of oscillations of the reference oscillating signal to a reference number using a comparator and changing a state of an output of the comparator when the number of oscillations of the reference oscillating signal equals or exceeds the reference number.

27. The method of claim 26, wherein generating the reference oscillating signal comprises using an arbitrary frequency reference oscillator, and wherein the method further comprises providing the reference number from the arbitrary frequency reference oscillator to the comparator.