Inductor and capacitor-based clock generator and timing/frequency reference

• US 7,872,541 B2
• Filed: 12/29/2008
• Issued: 01/18/2011
• Est. Priority Date: 03/22/2004
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Mobius Microsystems, Inc. (Renesas Electronics Corporation)
• Inventors: McCorquodale, Michael Shannon, Pernia, Scott Michael, Kubba, Sundus
• Primary Examiner(s): Chang; Joseph
• Application Number:
  US12/345,280
• Publication Number:
  US 20090167444A1
• Time in Patent Office: 750 Days
• Field of Search: 331/44, 331/117, 331/158, 331/34, 331/117.R, 331/167
• US Class Current: 331/167
• CPC Class Codes: G06F 1/04 Generating or distributing clock signals or signals derived directly therefrom
• CPC Class Codes: G06F 1/08 Clock generators with changeable or programmable clock frequency
• CPC Class Codes: H03B 2201/025 the means being an electronic switch for switching in or out oscillator elements
• CPC Class Codes: H03B 5/06 Modifications of generator to ensure starting of oscillations
• CPC Class Codes: H03B 5/1212 the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1221 the amplifier comprising multiple amplification stages connected in cascade
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/124 the means comprising a voltage dependent capacitance
• CPC Class Codes: H03J 1/0008 using a central processing unit, e.g. a microprocessor digital tuning in general H03J5/0245
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03L 1/022 by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence
• CPC Class Codes: H03L 3/00 Starting of generators
• CPC Class Codes: H03L 7/08 Details of the phase-locked loop
• CPC Class Codes: H03L 7/0812 and where no voltage or current controlled oscillator is used
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop

Abstract

In various embodiments, the invention provides a clock generator and/or a timing and frequency reference comprising an LC oscillator with a frequency controller to control and provide a stable resonant frequency. Such stability is provided over variations in a selected parameter such as temperature and fabrication process variations. The various apparatus embodiments include a sensor to provide a signal in response to at least one parameter of a plurality of parameters; and a frequency controller to modify the resonant frequency in response to the second signal. In exemplary embodiments, the sensor is implemented as a current source responsive to temperature fluctuations, and the frequency controller is implemented as a plurality of controlled reactance modules which are selectively couplable to the oscillator or to one or more control voltages. The controlled reactance modules may include fixed or variable capacitances or inductances, and may be binary weighted. Arrays of resistive modules are also provided, to generate one or more control voltages.

Claims

1. An apparatus for providing a first reference signal, the apparatus comprising:

a control voltage generator to provide a control voltage; and

a reference oscillator to provide the first reference signal having a calibrated first frequency, the reference oscillator comprising an inductor and at least one reactance module to provide a selected reactance in response to the control voltage to maintain the calibrated first frequency within a predetermined frequency range.

2. The apparatus of claim 1, further comprising:

a square-wave generator coupled to the reference oscillator, the square-wave generator to convert the first reference signal into a square-wave reference signal or clock signal having a substantially equal duty cycle.

3. The apparatus of claim 1, wherein the reference oscillator has at least one configuration of the following configurations:

a double-balanced, differential LC configuration;

a differential n-MOS cross-coupled topology;

a differential p-MOS cross-coupled topology;

a single-ended Colpitts LC configuration;

a single-ended Hartley LC configuration;

a differential, common base Colpitts LC configuration;

a differential, common collector Colpitts LC configuration;

a differential, common base Hartley LC configuration;

a differential, common collector Hartley LC configuration;

a single-ended Pierce LC oscillator, or a quadrature LC oscillator configuration.

4. The apparatus of claim 1, wherein the inductor is an active inductor or is a passive inductor comprising a coil formed in a CMOS-compatible conductive layer.

5. The apparatus of claim 1, wherein the at least one reactance module comprises:

a variable capacitor to provide a corresponding capacitance in response to the control voltage.

6. The apparatus of claim 1, further comprising:

a coefficient register to store at least one coefficient.

7. The apparatus of claim 6, wherein the at least one reactance module comprises:

a switch coupled to the coefficient register and switchable in response to the at least one coefficient; and

a fixed capacitor coupled to the switch, the fixed capacitor to provide a corresponding capacitance when switched to a corresponding voltage.

8. The apparatus of claim 7, wherein the corresponding voltage is at least one of the following voltages:

a ground potential, a control voltage, or a power rail voltage.

9. The apparatus of claim 7, wherein the at least one coefficient is determined post-fabrication by calibration to a second, reference frequency signal.

10. The apparatus of claim 7, wherein the at least one reactance module comprises:

a switch coupled to the coefficient register and switchable in response to the at least one coefficient; and

a variable capacitor coupled to the switch and to the control voltage generator, the variable capacitor to provide a corresponding capacitance in response to the control voltage.

11. The apparatus of claim 1, wherein the reference oscillator further comprises an amplifier, the amplifier comprising a variable current source to provide a corresponding current in response to ambient or operating temperature.

12. The apparatus of claim 1, wherein the predetermined frequency range corresponds to a spread-spectrum frequency range.

13. The apparatus of claim 1, wherein the predetermined frequency range is selectable post-fabrication.

14. The apparatus of claim 1, wherein the predetermined frequency range is substantially constant at the calibrated first frequency.

15. The apparatus of claim 1, wherein the at least one reactance module further comprises:

at least one variable capacitor to provide a corresponding capacitance in response to the control voltage; and

at least one fixed capacitor to provide a corresponding capacitance when switched to a corresponding voltage.

16. The apparatus of claim 1, wherein the control voltage is variable in response to a corresponding temperature variation.

17. The apparatus of claim 1, wherein the control voltage is variable in response to a parameter of a plurality of variable parameters, the plurality of variable parameters comprising at least one of the following parameters:

temperature, fabrication process, voltage, age, and frequency.

18. The apparatus of claim 17, wherein the control voltage generator further comprises:

a current source to provide a parameter-dependent current to generate the control voltage.

19. The apparatus of claim 18, wherein the current source has at least one complementary to absolute temperature (CTAT) configuration, proportional to absolute temperature (PTAT) configuration, or proportional to absolute temperature squared (PTAT²) configuration.

20. The apparatus of claim 1, further comprising:

a divider or a locking circuit to provide a second reference signal having a second frequency less than or equal to the calibrated first frequency.

21. The apparatus of claim 20, further comprising:

control circuitry coupled to the divider or locking circuit, the control circuitry to provide a control signal to modify a divide ratio to provide a spread-spectrum second reference signal.

22. The apparatus of claim 20, further comprising:

control circuitry coupled to the divider or locking circuit, the control circuitry to provide a control signal to selectively switch the reactance module to modify the first frequency to provide a spread-spectrum first reference signal.

23. An apparatus for providing an output reference signal, the apparatus comprising:

a reference oscillator comprising an inductor and a capacitor, the reference oscillator to provide a first reference signal having a first frequency;

a sensor to provide a second signal in response to a parameter; and

a phase-locked loop coupled to the reference oscillator to phase lock to the first reference signal and provide the output reference signal having an output frequency determined from the first frequency and a divide ratio.

24. The apparatus of claim 23, further comprising:

a control voltage generator to provide a control voltage in response to the second signal.

25. The apparatus of claim 24, wherein the reference oscillator further comprises:

a reactance to provide a corresponding reactance in response to the control voltage to maintain the first frequency within a predetermined frequency range.

26. The apparatus of claim 23, further comprising:

control logic to provide at least one coefficient in response to the second signal.

27. The apparatus of claim 26, further comprising:

a reactance;

a switch to switch the reactance to a corresponding voltage in response to the at least one coefficient to maintain the first frequency within a predetermined frequency range.

28. The apparatus of claim 27, wherein the corresponding voltage is at least one of the following voltages:

a ground potential, a control voltage, or a power rail voltage.

29. The apparatus of claim 23, wherein the parameter is at least one of the following parameters:

temperature, fabrication process, voltage, age, and frequency.

30. The apparatus of claim 23, wherein the oscillator has at least one configuration of the following configurations:

a double-balanced, differential LC configuration;

a differential n-MOS cross-coupled topology;

a differential p-MOS cross-coupled topology;

a single-ended Colpitts LC configuration;

a single-ended Hartley LC configuration;

a differential, common base Colpitts LC configuration;

a differential, common collector Colpitts LC configuration;

a differential, common base Hartley LC configuration;

a differential, common collector Hartley LC configuration;

a single-ended Pierce LC oscillator, or a quadrature LC oscillator configuration.

31. The apparatus of claim 23, wherein the sensor comprises a variable current source to provide a corresponding current in response to ambient or operating temperature.

32. An apparatus for providing an output reference signal, the apparatus comprising:

a reference oscillator comprising an inductor and a capacitor, the reference oscillator to provide a first reference signal having a calibrated first frequency;

a sensor to provide a second signal in response to a parameter;

a variable capacitor to provide a selected capacitance in response to a control voltage to maintain the calibrated first frequency within a predetermined frequency range; and

a divider coupled to the reference oscillator to provide the output reference signal having an output frequency determined from the calibrated first frequency and a divide ratio.

33. The apparatus of claim 32, further comprising:

control circuitry to provide a control signal to the divider to modify a divide ratio to provide a spread-spectrum output reference signal.

34. The apparatus of claim 32, wherein the sensor further comprises:

a current source to provide a parameter-dependent current for generation of the control voltage, wherein the control voltage is variable in response to the variation of the parameter.

35. The apparatus of claim 34, wherein the parameter is temperature, and wherein the current source has at least one complementary to absolute temperature (CTAT) configuration, or proportional to absolute temperature (PTAT) configuration, or proportional to absolute temperature squared (PTAT²) configuration.

36. The apparatus of claim 32, wherein the variable capacitor is coupled directly to the reference oscillator or is switchable to the reference oscillator.

37. The apparatus of claim 32, wherein the reference oscillator has at least one configuration of the following configurations:

a double-balanced, differential LC configuration;

a differential n-MOS cross-coupled topology;

a differential p-MOS cross-coupled topology;

a single-ended Colpitts LC configuration;

a single-ended Hartley LC configuration;

a differential, common base Colpitts LC configuration;

a differential, common collector Colpitts LC configuration;

a differential, common base Hartley LC configuration;

a differential, common collector Hartley LC configuration;

a single-ended Pierce LC oscillator, or a quadrature LC oscillator configuration.

38. The apparatus of claim 32, wherein the reference oscillator further comprises:

a plurality of switchable, controlled reactance modules, each reactance module of the plurality of reactance modules to provide a corresponding reactance in response to a corresponding control signal.

39. The apparatus of claim 38, further comprising:

control circuitry coupled to the plurality of controlled reactance modules, the control circuitry to provide a control signal to the plurality of controlled reactance modules to selectively switch the plurality of controlled reactance modules to modify the first frequency to provide a spread-spectrum first reference signal.

40. The apparatus of claim 38, further comprising:

a coefficient register coupled to the plurality of switchable, controlled reactance modules, the coefficient register to store a plurality of coefficients and to provide a corresponding coefficient as the control signal to control switching of a corresponding controlled reactance module.

41. The apparatus of claim 40, wherein the plurality of switchable, controlled reactance modules further comprise:

a plurality of switches coupled to the coefficient register; and

a second plurality of variable capacitors correspondingly coupled to the plurality of switches, the plurality of variable capacitors to provide a selected capacitance in response to the control voltage.

42. The apparatus of claim 40, wherein the plurality of switchable, controlled reactance modules further comprise:

a plurality of switches coupled to the coefficient register; and

a plurality of fixed capacitors correspondingly coupled to the plurality of switches, the plurality of fixed capacitors to provide a selected capacitance.

43. The apparatus of claim 32, further comprising:

a control voltage generator to provide the control voltage is response to the second signal.

44. An apparatus for providing an output reference signal, the apparatus comprising:

a control voltage generator to provide a control voltage;

a reference oscillator to provide a first reference signal having a resonant frequency, the reference oscillator comprising an inductor and at least one variable capacitor to provide a selected reactance in response to the control voltage to maintain the resonant frequency substantially constant during a variation of at least one parameter in a first operating mode; and

a frequency divider to provide the output reference signal having an output frequency determined from the resonant frequency and a divide ratio.

45. The apparatus of claim 44, further comprising:

a sensor to provide a sensor signal in response to the variation of the at least one parameter; and

control circuitry coupled to the control voltage generator to generate a variable control voltage is response to the sensor signal.

46. The apparatus of claim 44, further comprising:

a user interface for input or selection of the divide ratio.

47. The apparatus of claim 44, further comprising:

control circuitry to modify the divide ratio to provide a spread-spectrum second reference signal in a second, spread-spectrum operating mode.

48. The apparatus of claim 44, wherein the reference oscillator further comprises:

a plurality of switchable, controlled reactance modules, each reactance module of the plurality of reactance modules to provide a selected reactance in response to a corresponding coefficient.

49. The apparatus of claim 48, further comprising:

control circuitry coupled to the plurality of controlled reactance modules, the control circuitry to provide a control signal to the plurality of controlled reactance modules to selectively switch the plurality of controlled reactance modules to modify the first frequency to provide a spread-spectrum first reference signal in a second, spread-spectrum operating mode.

50. The apparatus of claim 44, wherein the at least one parameter is temperature, wherein the control voltage generator comprises at least one resistive module;

and wherein the sensor is a temperature-dependent current source coupled to the at least one resistive module to generate a variable control voltage is response to temperature variation.