A circuit device includes a phase comparator that performs phase comparison between an input signal based on an oscillation signal and a reference signal, a processor that performs a digital signal process on phase comparison result data which is a result of the phase comparison so as to generate frequency control data, and an oscillation signal generation circuit that generates the oscillation signal having an oscillation frequency which is set on the basis of the frequency control data. The processor performs the digital signal process by using data used when a hold-over state is ended in a case where the hold-over state occurs due to the absence or the abnormality of the reference signal, and then the hold-over state is ended.

An oscillator includes a package having a first side, a second side, a third side, and a fourth side, a resonator and an oscillation circuit disposed in the package, an output terminal arranged along the first side of the package, and outputting a clock signal generated by the oscillation circuit, and a control terminal arranged along the second side of the package, and supplied with a digital control signal adapted to update an operation state of the oscillation circuit.

A circuit device includes an oscillation signal generation circuit that generates an oscillation signal having an oscillation frequency, the oscillation frequency being a frequency set by using frequency control data, and a processor that is configured to perform a signal process on input frequency control data, and. The processor is configured to acquire the frequency control data from which an environmental change component is removed of the environmental change component and an aging change component by using environmental change component information, and perform aging correction on the basis of the frequency control data from which the environmental change component is removed.

A circuit device includes an oscillation signal generation circuit that generates an oscillation signal having an oscillation frequency set by the frequency control data by using a resonator, and a processor that is configured to perform a signal process on input frequency control data to output frequency control data. The processor is configured to obtain a pre-estimated value x^.sup.(k) at a time step k by adding a post-estimated value x^(k1) and a correction value D(k1) at a time step k1 together during a process of updating a pre-estimated value in a Kalman filter process, and perform aging correction on the frequency control data on the basis of a result of the Kalman filter process.

This temperature-compensated crystal oscillator includes: a crystal resonator; first and second MOS-type variable capacitance elements, each having one end electrically connected to first or second electrodes of the crystal resonator; and a temperature compensation circuit that applies a temperature compensation voltage, which changes in accordance with a temperature, to other ends of the first and second MOS-type variable capacitance elements. The first MOS-type variable capacitance element includes a first back gate provided within a semiconductor substrate, and an N-type first gate electrode provided above the first back gate with an insulating film interposed therebetween; and the second MOS-type variable capacitance element includes a second back gate provided within the semiconductor substrate and having the same conductivity type as the first back gate, and a P-type second gate electrode provided above the second back gate with an insulating film interposed therebetween.

A circuit device includes an oscillation signal generation circuit that generates an oscillation signal having an oscillation frequency using a resonator, the oscillation frequency being a frequency set by using frequency control data, and a processor configured to perform a signal process on input frequency control data based on a phase comparison result between an input signal based on the oscillation signal and a reference signal. The processor is configured to estimate a true value for an observed value of the frequency control data based on the phase comparison result through a Kalman filter process in a period before a hold-over state is detected, and generate aging-corrected frequency control data, in a case where the hold-over state is detected, by holding the true value at a timing corresponding to a timing of detecting the hold-over state, and by performing a calculation based on the true value.

An oscillator includes: an oscillation stage circuit that is connected between a first electrode and a second electrode of a resonator and performs an oscillation operation; a variable capacitance element that is connected to the first or second electrode of the resonator and adjusts an oscillation frequency; a bandgap reference circuit that generates a reference voltage having magnitude, which changes depending on the temperature, by using a resistor inserted in a current path through which a current having magnitude, which changes depending on the temperature flows; and a bias current generating circuit that generates a bias current of the oscillation stage circuit based on the reference voltage, and that, thereby, reduces a change in the oscillation frequency due to the temperature dependence of the impedance of the resonator or the temperature dependence of the sensitivity of the variable capacitance element.

A circuit device includes a first PLL circuit to which a first clock signal having a first clock frequency generated using a first resonator and a reference clock signal are input, and which performs phase synchronization between the first clock signal and the reference clock signal, a second PLL circuit to which a second clock signal generated using a second resonator and having a second clock frequency different from the first clock frequency and the reference clock signal are input, and which performs phase synchronization between the second clock signal and the reference clock signal, and a time-to-digital conversion circuit adapted to convert time into a digital value using the first clock signal and the second clock signal.

A circuit device includes an oscillation circuit which is electrically coupled to a first node to electrically be coupled to one end of a resonator and a second node to electrically be coupled to another end of the resonator, and is configured to oscillate the resonator to generate an oscillation signal, and a waveform shaping circuit which is coupled to the first node, to which the oscillation signal is input from the first node, and which is configured to output a clock signal obtained by performing waveform shaping on the oscillation signal, and a duty adjustment circuit configured to supply the first node with a bias voltage which is variably adjusted based on adjustment data to thereby adjust a duty ratio of the clock signal.

A oscillator includes a substrate having a first surface and a second surface, a first wiring layer and a second wiring layer disposed respectively on the first and second surfaces, and a plurality of through holes electrically connecting the first and second wiring layers to each other, a resonator disposed above the first surface of the substrate, and having a resonator element, a pair of electrodes sandwiching the resonator element, and a pair of terminals adapted to electrically connect the pair of electrodes to the first electrode layer, and at least one semiconductor device disposed on the second surface of the substrate, adapted to generate an oscillation signal, and having first and second terminals electrically connected respectively to the pair of terminals of the resonator via the second wiring layer and the first wiring layer, and a third terminal supplied with a digital control signal, wherein a distance between each of the first and second terminals and the pair of terminals of the resonator is shorter than a distance between the third terminal and the pair of terminals of the resonator.