Single insertion trimming of highly accurate reference oscillators

A method of calibrating an oscillator for frequency-accurate, frequency-stable operation across a temperature range, the oscillator comprising a frequency determining element, circuitry responsive to a digital frequency setting value to cause a change in an output frequency of the oscillator, and circuitry responsive to a digital phase setting value to cause a specified phase across the frequency determining element, the method comprising:

• determining frequency differences at different instants of time between the output frequency of the oscillator and a reference frequency;
• under a temperature condition and under control of a first control loop, applying temperature modulation to the oscillator, determining a temperature sensitivity of the output frequency of the oscillator, and searching for and identifying a final digital phase setting value that results in a temperature sensitivity that matches a predetermined criterion;
• and
• under said temperature condition and under control of a second control loop, determining a final digital frequency setting value that minimizes the frequency differences;
• wherein the final digital phase setting value and the final digital frequency setting value simultaneously satisfy a frequency accuracy requirement and a requirement of frequency stability over a specified temperature range.

An apparatus comprising:

• an oscillator comprising a frequency determining element;
• circuitry responsive to a digital frequency setting value to cause a change in an output frequency of the oscillator;
• circuitry responsive to a digital phase setting value to cause a specified phase across the frequency determining element;
• circuitry to determine frequency differences at different instants of time between the output frequency of the oscillator and a reference frequency;
• control logic;
• a first control loop controlled by the control logic to, under a temperature condition, apply temperature modulation to the oscillator, determine a temperature sensitivity of the output frequency of the oscillator, and search for and identifying a final digital phase setting value that results in a temperature sensitivity that matches a predetermined criterion;
• and
• a second control loop controlled by the control logic to, under the temperature condition, determine a final digital frequency setting value that minimizes the frequency differences;
• wherein the final digital phase setting value and the final digital frequency setting value simultaneously satisfy a frequency accuracy requirement and a requirement of frequency stability over temperature.

A method of calibrating an oscillator circuit fabricated on an integrated circuit and responsive to a frequency setting signal to cause a change in an output frequency of the oscillator circuit, comprising:

• applying temperature modulation to the oscillator;
• measuring results of the temperature modulation;
• processing the measured results to estimate at least first and second temperature derivatives of the output frequency;
• using the estimates of the temperature derivatives of the output frequency to determine a plurality of coefficients of a temperature compensation function with an objective of causing temperature sensitivity of the output frequency to match a predetermined criterion;
• and
• storing the plurality of coefficients;
• wherein the oscillator circuit is configured to, during operation, use the plurality of coefficients and a temperature measurement to produce a compensated frequency setting signal that compensates the output frequency in accordance with the temperature measurement.

An oscillator circuit comprising an oscillator and calibration circuitry and responsive to a frequency setting signal to cause a change in an output frequency of the oscillator circuit, the calibration circuitry comprising:

• temperature modulation circuitry comprising heaters and a feedback control loop for applying temperature modulation to the oscillator;
• measurement circuitry to measure results of the temperature modulation;
• calculation circuitry to use results of the temperature modulation to determine a plurality of coefficients of a temperature compensation function;
• storage to store the plurality of coefficients;
• temperature measurement circuitry;
• and
• compensation circuitry to, during operation, use the plurality of coefficients and a temperature measurement to produce as a compensated frequency setting signal that compensates the output frequency in accordance with the temperature measurement.

A method of validating temperature performance of an oscillator circuit and responsive to a frequency setting signal to cause a change in an output frequency of the oscillator circuit, comprising:

• applying temperature modulation to the oscillator;
• measuring results of the temperature modulation;
• processing the measured results to estimate at least first and second temperature derivatives of the output frequency;
• and
• using the estimates of the temperature derivatives of the output frequency to determine whether or not temperature sensitivity of the output frequency matches a predetermined criterion.