Temperature compensated crystal oscillator

• US 20060071728A1
• Filed: 09/30/2004
• Published: 04/06/2006
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chen, Chun-Ying
• Granted Patent: US 7,161,443 B2
• Time in Patent Office: Days
• US Class Current: 331/158
• CPC Class Codes: H03L 1/027 by using frequency conversion means which is variable with temperature, e.g. mixer, frequency divider, pulse add/substract logic circuit H03L1/023, H03L1/026 take precedence
• CPC Class Codes: H03L 7/081 provided with an additional controlled phase shifter H03L7/0998 takes precedence
• CPC Class Codes: H03L 7/183 a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number H03L7/1806 takes precedence

Abstract

An environmental-compensated oscillator includes a reference clock waveform generator; a phase locked loop receiving the reference clock waveform and outputting a phase locked clock waveform; and a sensor outputting a voltage corresponding to an environmental parameter of the generator. The voltage is used by the PLL to compensate the phase locked clock waveform. The PLL includes a phase detector, a charge pump coupled to an output of the phase detector, a low pass filter coupled to an output of the charge pump, a voltage controlled oscillator (“VCO”) coupled to an output of the low pass filter, and a feedback path coupled between an output of the VCO and the phase detector, wherein the feedback path includes a phase rotator capable of fine tuning an output frequency of the VCO responsive to a frequency of an input clock. An accumulator is coupled to the phase rotator and supplies the input clock to the phase rotator. The phase rotator finely tunes the VCO output frequency. An analog-to-digital converter converts the voltage to a digital representation. The digital representation is mapped to a frequency adjustment for use by the PLL for the compensation. The environmental parameter is any of temperature, stress and power supply voltage.

Claims

1. A temperature-compensated oscillator comprising:

a crystal oscillator outputting a reference clock;

a phase locked loop (PLL) receiving the reference clock and outputting a phase locked clock waveform;

a temperature sensor outputting a voltage corresponding to a temperature of the crystal oscillator;

wherein the voltage is used by the PLL to temperature-compensate the phase locked clock waveform.

2. The temperature-compensated oscillator of claim 1, wherein the PLL comprises:

a phase detector;

a charge pump coupled to an output of the phase detector;

a low pass filter coupled to an output of the charge pump;

a voltage controlled oscillator (“

VCO”

) coupled to an output of the low pass filter; and

a feedback path coupled between an output of the VCO and the phase detector, wherein the feedback path includes a phase rotator capable of fine tuning an output frequency of the VCO responsive to a frequency of an input clock.

3. The temperature-compensated oscillator of claim 2, wherein the feedback path further comprises an accumulator coupled to the phase rotator, wherein the accumulator supplies the input clock to the phase rotator.

4. The temperature-compensated oscillator of claim 3, wherein the phase rotator finely tunes the VCO output frequency upon application of the input clock.

5. The temperature-compensated oscillator of claim 1, further comprising an analog-to-digital converter for converting the voltage to a digital representation.

6. The temperature-compensated oscillator of claim 5, further comprising mapping of the digital representation to a frequency adjustment for use by the PLL for the temperature compensation.

7. A method of temperature-stabilizing an oscillator comprising:

receiving an input reference signal having a reference phase and frequency;

generating a voltage controlled oscillator (VCO) output signal based on the input reference signal;

feeding the VCO output signal through the feedback path to the phase detector;

receiving a temperature input in the feedback path; and

phase rotating the VCO output signal in the feedback path based on the temperature to perform fine frequency tuning the VCO output signal.

8. The method of claim 7, further comprising the step of adjusting a divider ratio of a frequency divider in the feedback path to perform coarse frequency tuning.

9. The method of claim 7, further comprising the step of adjusting the reference signal frequency to perform coarse frequency tuning.

10. The method of claim 7, further comprising converting the temperature input to a digital representation.

11. The method of claim 10, further comprising mapping the digital representation to a frequency adjustment for use by the feedback path for temperature compensation.

12. A environmental-compensated oscillator comprising:

a reference clock waveform generator;

a phase locked loop (PLL) receiving the reference clock waveform and outputting a phase locked clock waveform;

a sensor outputting a voltage corresponding to an environmental parameter of the generator;

wherein the voltage is used by the PLL to compensate the phase locked clock waveform.

13. The oscillator of claim 12, wherein the PLL comprises:

a phase detector;

a charge pump coupled to an output of the phase detector;

a low pass filter coupled to an output of the charge pump;

a voltage controlled oscillator (“

VCO”

) coupled to an output of the low pass filter; and

a feedback path coupled between an output of the VCO and the phase detector, wherein the feedback path includes a phase rotator capable of fine tuning an output frequency of the VCO responsive to a frequency of an input clock.

14. The oscillator of claim 13, wherein the feedback path further comprises an accumulator coupled to the phase rotator, wherein the accumulator supplies the input clock to the phase rotator.

15. The oscillator of claim 14, wherein the phase rotator finely tunes the VCO output frequency upon application of the input clock.

16. The oscillator of claim 12, further comprising an analog-to-digital converter for converting the voltage to a digital representation.

17. The oscillator of claim 16, further comprising mapping of the digital representation to a frequency adjustment for use by the PLL for the compensation.

18. The oscillator of claim 12, wherein the environmental parameter is any of temperature, stress and power supply voltage.