Method for calibrating a temperature sensitive oscillator
AssigneeDallas Semiconductor Corporation
InventorsDouglas Gene Cole, Ranganath Bagade, Titkwan Hui
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Abstract
A temperature compensated crystal oscillation circuit adapted to be contained within a small device package and providing an output frequency accuracy of approximately +/−2 ppm over a temperature range or less than 2 minutes per year over the temperature range. The device includes crystal and a single integrated circuit wherein the integrated circuit has a temperature sensing circuit with a digital output, control circuitry, a memory circuit and a switched capacitor array for compensating the oscillation of the crystal oscillator over temperature.
Claims5
A method for calibrating a temperature compensated oscillator, the method comprising the steps of:
- storing during the manufacturing process a table of fixed capacitance values;
- operating the temperature compensated oscillator at a first temperature to generate a first clock signal at a first clock rate;
- adjusting a parameter of a capacitance load to a first value such that the generated first clock signal is varied from the first clock rate to a preferred clock rate;
- storing a first indicator corresponding to the first value and the first temperature;
- operating the temperature compensated oscillator at a second temperature to generate a second clock signal at a second clock rate;
- selecting from at least two possible capacitance loads, from a plurality of prestored fixed capacitance values to a second value, such that the generated second clock signal is varied from the second clock rate to the preferred clock rate;
- and
- storing a second indicator corresponding to the second value and the second temperature.
Dependencies are inferred from the claim text.