Low-latency start-up for a monolithic clock generator and timing/frequency reference

• US 7,545,227 B2
• Filed: 10/28/2007
• Issued: 06/09/2009
• Est. Priority Date: 03/22/2004
• Status: Expired due to Fees

• 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): MIS, DAVID C
• Application Number:
  US11/926,013
• Publication Number:
  US 20080100392A1
• Time in Patent Office: 590 Days
• Field of Search: 331/117.R, 331/117.FE, 331/117.D, 331172-173, 331175-176, 331/177.R, 331/177.V, 331/179
• US Class Current: 331/173
• CPC Class Codes: H03B 2200/0038 including a current mirror
• CPC Class Codes: H03B 2200/005 including measures to switch a capacitor
• CPC Class Codes: H03B 2200/0098 having a balanced output signal
• 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 5/06 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 5/1228 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 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03K 23/66 with a variable counting base, e.g. by presetting or by adding or suppressing pulses
• CPC Class Codes: H03K 23/662 by adding or suppressing pulses
• CPC Class Codes: H03L 1/00 Stabilisation of generator output against variations of physical values, e.g. power supply
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 3/00 Starting of generators
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or 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
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence
• CPC Class Codes: H03L 7/24 using a reference signal directly applied to the generator

Abstract

An apparatus, system and method are provided for low-latency start-up of a free-running harmonic oscillator. The exemplary apparatus embodiment comprises a first and second current sources to generate first and second currents; a bias current monitor adapted to detect a magnitude of the second current and to provide a control signal when the magnitude of the second current is equal to or greater than a predetermined magnitude; and a bias controller adapted to switch the first current from the oscillator and to switch the second current to the oscillator in response to the control signal. a reference voltage generator, a comparator, and a bias controller. Exemplary embodiments include reference voltage generator, a comparator, and a bias controller.

Claims

1. A start-up apparatus for a free-running harmonic oscillator, the apparatus comprising:

a first current source to provide a first current;

a second current source to provide a second current, the second current proportional to temperature;

a bias current monitor coupled to the first current source and the second current source, the bias current monitor to detect a magnitude of the second current and to provide a control signal when the magnitude of the second current is equal to or greater than a predetermined magnitude; and

a bias controller coupled to the bias current monitor, the bias controller to switch the first current from the oscillator and to switch the second current to the oscillator in response to the control signal.

2. The apparatus of claim 1, wherein the first current source further comprises:

a switchable resistive module coupled to the bias controller.

3. The apparatus of claim 1, wherein the bias current monitor is to detect the magnitude of the second current as a voltage change, as a current change, or as a resistance change.

4. The apparatus of claim 1, wherein the second 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.

5. The apparatus of claim 4, wherein the second current source is coupled through a current mirror and a switch to the bias controller.

6. The apparatus of claim 4, wherein the bias current monitor further comprises:

a voltage divider coupled between a first voltage and a second voltage to provide a first reference voltage; and

a resistive module coupled between the first voltage and the second voltage and further coupled through a current mirror to the second current source, the resistive module to provide a second reference voltage generated as a voltage change across a resistor of the resistive module.

7. The apparatus of claim 1, wherein the bias current monitor further comprises:

a resistive module coupled to the second current source, the resistive module to provide a voltage signal responsive to the second current; and

a comparator coupled to the resistive module and to a substantially stable predetermined control voltage, the comparator to provide the control signal when the voltage signal exceeds the predetermined control voltage.

8. The apparatus of claim 1, wherein the bias current monitor comprises one or more of the following:

a voltage divider, a bandgap reference, a current detector, a voltage regulator, or a voltage detector.

9. The apparatus of claim 1, wherein the bias controller further is to switch the first current to the oscillator upon start-up of the harmonic oscillator from a low power or no power mode.

10. A method of providing low-latency start-up for a harmonic oscillator, the method comprising:

generating a first current;

generating a second current, the second current having a latency to reach a steady-state, and the second current proportional to temperature;

generating a first reference voltage and a second reference voltage;

comparing the first reference voltage to the second reference voltage;

when the second reference voltage is greater than the first reference voltage, providing the first current to the oscillator; and

when the second reference voltage is not greater than the first reference voltage, providing the second current to the oscillator.

11. The method of claim 10, further comprising:

generating the first current through a switchable resistive module.

12. The method of claim 11, further comprising:

generating the second current through a temperature-dependent current source.

13. The method of claim 12, wherein the temperature-dependent 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.

14. The method of claim 13, wherein the second reference voltage is generated as a variable voltage across a resistor from a changing temperature-dependent current, and wherein the first reference voltage is substantially stable.

15. A system for low-latency start-up of a free-running harmonic oscillator, the system comprising:

a harmonic oscillator;

a reference voltage generator to generate a first reference voltage and a second reference voltage;

a comparator coupled to the reference voltage generator, the comparator to compare the first reference voltage to the second reference voltage and to provide a first comparison signal when the second reference voltage is greater than the first reference voltage and to provide a second comparison signal when the second reference voltage is not greater than the first reference voltage;

a bias controller coupled to the comparator, the bias controller to switch a first current to the harmonic oscillator in response to the first comparison signal and to switch a second current to the oscillator in response to the second comparison signal; and

a current source to provide the second current, the second current proportional to temperature.

16. The system of claim 15, further comprising:

a switchable resistive module coupled to the bias controller, the switchable resistive module to provide the first current.

17. The system of claim 15, 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.

18. The system of claim 15, wherein the current source is coupled through a current mirror and a switch to the bias controller.

19. The system of claim 15, wherein the reference voltage generator further comprises:

a voltage divider coupled between a first voltage and a second voltage to provide the first reference voltage; and

a resistive module coupled between the first voltage and the second voltage and further coupled through a current mirror to the current source.

20. The system of claim 19, wherein the second reference voltage is generated as a voltage change from a temperature-dependent current across a resistor of the resistive module.

21. The system of claim 15, wherein the first reference voltage is substantially stable, and wherein the second reference voltage changes as the second current approaches steady-state.

22. A start-up apparatus for a free-running harmonic oscillator, the apparatus comprising:

a reference voltage generator to generate a first reference voltage and a second reference voltage;

a comparator coupled to the reference voltage generator, the comparator to compare the first reference voltage to the second reference voltage and to provide a first comparison signal when the second reference voltage is greater than the first reference voltage and to provide a second comparison signal when the second reference voltage is not greater than the first reference voltage;

a bias controller coupled to the comparator, the bias controller to switch a first current to the oscillator in response to the first comparison signal and to switch a second current to the oscillator in response to the second comparison signal; and

a temperature-dependent current source to provide the second current, the second current proportional to temperature.

23. The apparatus of claim 22, further comprising:

a switchable resistive module coupled to the bias controller, the switchable resistive module to provide the first current.

24. The apparatus of claim 23, wherein the temperature-dependent 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.

25. The apparatus of claim 24, wherein the temperature-dependent current source is coupled through a current mirror and a switch to the bias controller.

26. The apparatus of claim 24, wherein the reference voltage generator further comprises:

a voltage divider coupled between a first voltage and a second voltage to provide the first reference voltage; and

a resistive module coupled between the first voltage and the second voltage and further coupled through a current mirror to the temperature-dependent current source.

27. The apparatus of claim 26, wherein the second reference voltage is generated as a voltage change from a mirrored, temperature-dependent current across a resistor of the resistive module.

28. The apparatus of claim 22, wherein the comparator is an operational amplifier.