Patent ID: 7868710

Claim:
A digitally-controlled crystal oscillator (DCXO) circuit comprising: an active core; a first thermometer-coded switched-capacitor circuit (TCSCC) coupled to the active core and to a crystal, and adapted to: select at least one of a first plurality of capacitive elements based on a first control signal; and provide a first capacitance based on the selection of the at least one of the first plurality of capacitive elements; a second TCSCC coupled to the active core and to the crystal, and adapted to: select at least one of a second plurality of capacitive elements based on a second control signal; and provide a second capacitance based on the selection of the at least one of the second plurality of capacitive elements; and control circuitry adapted to, during a first fine tuning frequency step: provide the first control signal to increase the first capacitance; and provide the second control signal to decrease the second capacitance, wherein the active core, the crystal, the first TCSCC, and the second TCSCC form a crystal oscillator, which is adapted to provide an output signal having an output frequency based on the active core, the crystal, the first capacitance, and the second capacitance.