Patent ID: 7330079

Claim:
A control device to adjust a frequency of an adjustable-frequency oscillator, comprising: a first counter supplied with a stop-count value, the first counter coupled to the adjustable-frequency oscillator to count adjustable-frequency oscillator cycles divided by a frequency-dividing factor, wherein the first counter produces a stop signal when the first counter has counted a number of cycles of the adjustable-frequency oscillator equal to the stop-count; a reference oscillator; a second counter coupled to the first counter and to the reference oscillator to count reference oscillator cycles, wherein the second counter starts counting from an initial number at substantially the same time when the first counter starts counting and stops counting when the second counter receives the stop signal from the first counter to produce an end count in the second counter, the end count comprising a binary number; a resonant tank circuit coupled to the adjustable-frequency oscillator, the resonant tank circuit including a bank of capacitors and switches that are each coupled to a capacitor in the bank of capacitors, wherein the switches selectively couple capacitors in the bank of capacitors to the resonant tank circuit, and wherein capacitance of capacitors in the bank of capacitors form a sequence of capacitance substantially proportional to an integer-power-of-two sequence; and a switch selector circuit coupled to the switches in the resonant tank circuit to control the frequency of the adjustable-frequency oscillator, the switch selector circuit coupled to the second counter and to the switches in the resonant tank circuit, wherein the switch selector circuit controls the switches in the resonant tank circuit based on a ones complement of the binary number.