System and method of crystal oscillator temperature compensation for operation in extended temperature range

An oscillator circuit with temperature compensation, comprising:

• a crystal oscillator including a crystal that provides an oscillation signal;
• a temperature sensor coupled to said crystal of said crystal oscillator that provides a temperature sense signal indicative of a temperature of said crystal;
• a frequency synthesizer having an input receiving said oscillation signal, having an output providing a clock signal, and having an adjust input for adjusting a frequency of said clock signal;
• a memory that stores a plurality of compensation values including a plurality of nominal values of a nominal third order polynomial that defines a nominal frequency versus temperature relationship of a crystal design that represents a plurality of crystals, and further including a plurality of adjustment values derived from said plurality of nominal values and two temperature-frequency error points that were measured using said crystal;
• and
• a controller that determines a temperature value based on said temperature sense signal, that calculates a frequency offset using said temperature value and said plurality of compensation values to convert said nominal third order polynomial equation into a compensated third order polynomial equation defining a compensated frequency versus temperature relationship of said crystal, and that provides an adjust signal to said adjust input of said frequency synthesizer based on said frequency offset.

A method of performing temperature compensation based on temperature of a crystal, comprising:

• providing a clock signal based on an oscillation signal generated by oscillation of the crystal;
• storing compensation values including nominal values of a nominal third order polynomial equation that defines a nominal frequency versus temperature relationship of a crystal design that represents a plurality of crystals, and further including a plurality of adjustment values derived from the nominal values and two temperature-frequency error points that were measured using the crystal;
• receiving a sense voltage indicative of a temperature of the crystal and determining a temperature value based on the sense voltage;
• calculating a frequency offset using the temperature value and the plurality of compensation values to convert the nominal third order polynomial equation into a compensated third order polynomial equation defining a compensated frequency versus temperature relationship of the crystal;
• and
• adjusting the clock signal based on the frequency offset.