Methods of frequency versus temperature compensation of existing crystal oscillators
First Claim
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1. An adjustment circuit for adjusting a frequency of an output of an external crystal oscillator, the adjustment circuit comprising:
- an internal resonator that includes a temperature sensor and a frequency linearization circuit that is responsive to a temperature measured by the temperature sensor;
a primary PLL coupled to the internal resonator and configured to generate an output, which has a frequency that matches a nominal frequency of the external crystal oscillator; and
a secondary PLL coupled to the primary PLL and configured to receive the output and receive a feedback from the external crystal oscillator to correct the frequency of the output from the external crystal oscillator based on the temperature.
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Abstract
Methods for compensating the existing crystal oscillator frequencies in extended temperature ranges. Utilizing existing crystal oscillators on any system design which may have quartz crystals with associated circuitry to deliver frequency or timing reference signals and increasing the accuracy of such by additional circuitry.
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Citations
15 Claims
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1. An adjustment circuit for adjusting a frequency of an output of an external crystal oscillator, the adjustment circuit comprising:
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an internal resonator that includes a temperature sensor and a frequency linearization circuit that is responsive to a temperature measured by the temperature sensor; a primary PLL coupled to the internal resonator and configured to generate an output, which has a frequency that matches a nominal frequency of the external crystal oscillator; and a secondary PLL coupled to the primary PLL and configured to receive the output and receive a feedback from the external crystal oscillator to correct the frequency of the output from the external crystal oscillator based on the temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An adjustment circuit for adjusting a frequency of an output of an external crystal oscillator, the adjustment circuit comprising:
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a free running internal resonator; a temperature sensor coupled to the free running internal resonator and that includes a frequency linearization circuit that is configured to adjust a frequency of a reference signal generated by the free running internal resonator based on a temperature of the free running internal resonator sensed by the temperature sensor; a fractional PLL coupled to the free running internal resonator and the temperature sensor, wherein; the fractional PLL is configured to receive the reference signal generated by the free running internal resonator and frequency adjusted by the temperature sensor and the frequency linearization circuit; the fractional PLL includes a feedback configured to receive the output of the external crystal oscillator, and the fractional PLL is configured to generate an output that controls the frequency of the output of the external crystal oscillator based on the temperature, the output of the external crystal oscillator received at the feedback, and a free running signal received from the free running internal resonator. - View Dependent Claims (10)
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11. An adjustment circuit for adjusting a frequency of an output of an external crystal oscillator, the adjustment circuit comprising:
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an internal resonator having a temperature sensor and a frequency linearization circuit that is responsive to a temperature measured by the temperature sensor; a fractional PLL coupled to the internal resonator, wherein; the fractional PLL is configured to divide down the frequency of the output of the external crystal oscillator to a frequency of an output of the internal resonator, includes a feedback configured to receive the output of the external crystal oscillator, and configured to generate an output that controls the frequency of the output of the external crystal oscillator based on the temperature. - View Dependent Claims (12, 13, 14, 15)
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Specification