A circuit includes an oscillator having a driver and a resonator. The driver receives a supply voltage at a supply input and provides a drive output to drive the resonator to generate an oscillator output signal. A power converter receives an input voltage and generates the supply voltage to the supply input of the driver. A temperature tracking device in the power converter controls the voltage level of the supply voltage to the supply input of the driver based on temperature such that the supply voltage varies inversely to the temperature of the circuit.

Disclosed is an integrated circuit amplifier for use in a crystal oscillator. The circuit amplifier comprises a transistor; a voltage dependent capacitance circuit; and a node. The voltage dependent capacitance circuit comprises a device with a voltage dependent capacitance and a bias circuit. The node is connected to a terminal of the transistor and the integrated circuit amplifier is configured such that an intrinsic capacitance of the transistor is dependent on the mean voltage at the node. The node is connected to a terminal of the voltage dependent capacitance circuit and the integrated circuit amplifier is configured such that an effective capacitance of the node is dependent on the intrinsic capacitance of the transistor and the voltage dependent capacitance of said device. When in use, the voltage dependent capacitance circuit reduces the amount of change of the effective capacitance of the node when the mean voltage at the node changes.

The circuit device includes a first MOS transistor of a first conductivity type a source of which is coupled to a first power supply voltage node, a second MOS transistor of a second conductivity type a source of which is coupled to a second power supply voltage node, a first variable resistance circuit which is coupled between a drain of the first MOS transistor and an output node, and which includes a first switch, and a second switch coupled between the drain of the first MOS transistor and the second power supply voltage node. The control circuit performs control of making the first switch OFF and making the second switch ON when the clock signal fails to be output from the output node, and making the first switch ON and making the second switch OFF when the clock signal is output from the output node.

A crystal oscillator circuit that can be controlled for fast start-up and for efficient operation is disclosed. The control includes adjusting a voltage applied to a body terminal of a transistor in order to control the amplification of the crystal oscillator. The amplification can be increased, relative to a motional resistance of the crystal oscillator, at start-up to reduce a start-up time necessary for oscillation. The amplification can also be decreased in order to maintain oscillation after start-up more efficiently. In some implementations, the transistor for control is a fully depleted silicon on insulator (FDSOI) transistor that accommodates a wide range of body bias voltages.

In-package temperature is controlled with higher accuracy. To this end, a temperature control circuit includes a temperature sensor arranged in a package and detecting temperature in the package, a heater current detection circuit detecting a driving amount of a heater, a target temperature generation circuit generating a target temperature from an intended temperature of a resonator and a detection value of the driving amount detected by the heater current detection circuit, a heater current driver controlling the heater so that the detection temperature detected by the temperature sensor coincides with the target temperature, and an Nth-order correction circuit receiving the detection value of the driving amount detected by the heater current detection circuit or a signal based on the target temperature and cancelling influence of a second or higher order fluctuation component generated in the heater current detection circuit on temperature of the resonator.

A circuit and method for starting-up a crystal oscillator is described. A crystal resonator is configured to be coupled to a start-up circuit including an H-bridge circuit having a number of switches. A plurality of switch control signals are generated in response to detecting a zero-crossing event of the motional current in the crystal resonator. The switches of the H-bridge circuit are controlled by the switch control signals to apply a voltage to the terminals of the crystal resonator in a first polarity during a first switch control phase and a second opposite polarity during a second switch control phase. During a respective first subphase of the respective switch control phase, the plurality of switches are configured in a first configuration to couple the supply node to a respective crystal resonator terminal. During a respective second subphase of the respective switch control phase the plurality of switches are configured in a second configuration to couple the supply node to the respective crystal resonator terminal. The resistance between the supply node and the respective crystal resonator terminal is larger in the second configuration than the first configuration. A zero-crossing is detected during each respective second sub-phase.

An oscillator circuit includes an amplifying unit and a first feedback resistor. The amplifying unit includes an inverter at an input stage being connected to the one end of a crystal resonator, an inverter at an output stage being connected to the other end of the crystal resonator, and a linear amplifier. The linear amplifier is connected between an output terminal of the inverter at the input stage and an input terminal of the inverter at the output stage. The linear amplifier includes at least one inverter and a second feedback resistor. The second feedback resistor is connected in parallel to the at least one inverter. The linear amplifier has a conductance with a magnitude larger than a conductance of the inverter at the input stage and equal to or less than a conductance of the inverter at the output stage.

An enabling system that includes a controller and processing circuitry, is configured to enable an external oscillator that operates in one of single-ended, differential, and crystal modes. To enable the external oscillator, the controller is configured to detect a mode of operation of the external oscillator, and the processing circuitry is configured to operate in the detected mode. The controller detects the mode of operation of the external oscillator by sequentially initializing the processing circuitry to operate in the single-ended, differential, and crystal modes, and determining whether the current operating mode of the processing circuitry is same as the mode of operation of the external oscillator based on a clock signal outputted by the processing circuitry during the corresponding mode.

An oscillator circuit comprises a crystal oscillator and an inverter. The input of the inverter is connected to the first terminal of the crystal oscillator and the output of the inverter is connected to the second terminal of the crystal oscillator, oscillator circuit is arranged to operate the inverter in its linear operating region. An amplitude regulator has an input connected to the input of the inverter, arranged to provide a first supply current I.sub.AREG to the inverter, where the magnitude of the first supply current is inversely dependent on a magnitude of a voltage at the inverter input. A digital-to-analogue converter is arranged to provide a second supply current I.sub.DAC to the inverter having a magnitude determined by a digital signal applied to a digital input of the digital-to-analogue converter.

An oscillation circuit including an amplifier, a feedback resistor and a first switch circuit is provided. The amplifier inverts and amplifies an oscillation signal received from an input terminal thereof to provide an output oscillation signal at an output terminal thereof. The feedback resistor is coupled between the input terminal and the output terminal, and coupled with the first switch circuit in parallel. The first switch circuit conducts the input terminal to the output terminal in one of the following situations: (1) an input voltage of the oscillation signal is higher than an output voltage of the output oscillation signal by at least a first threshold value; and (2) the output voltage is higher than the input voltage by at least a second threshold value. The first switch circuit has a first on-state resistance smaller than a resistance of the feedback resistor.