An oscillator circuit includes a current source, an oscillating section, a first capacitor, and a setting section. The current source is coupled to a connection node and causes a current having a current value based on an input voltage to flow from a first power node to the connection node. The oscillating section is on a current path between the connection node and a second power node. The oscillating section oscillates at an oscillation frequency based on a current flowing through the current path. The first capacitor is between the connection node and the second power node. The first capacitor has a capacitance that varies in accordance with a voltage at the connection node. The setting section that performs variation operation based on the voltage at the connection node. The variation operation is operation of varying an impedance between the connection node and the second power node.

A clock distribution circuit may include a data clock generation circuit configured to be input a power source voltage and configured to generate an internal clock signal according to an external clock signal; and a global distribution circuit includes a first circuit and a second circuit coupled to a global line, configured to be input a power source voltage and configured to receive the internal clock signal through the first circuit and distribute the internal clock signal to an exterior of the clock distribution circuit through the second circuit, wherein a first bias voltage provided to the first circuit and a second bias voltage provided to the second circuit are controlled independently of each other.

A clock distribution circuit may include a data clock generation circuit configured to be input a power source voltage and configured to generate an internal clock signal according to an external clock signal; and a global distribution circuit includes a first circuit and a second circuit coupled to a global line, configured to be input a power source voltage and configured to receive the internal clock signal through the first circuit and distribute the internal clock signal to an exterior of the clock distribution circuit through the second circuit, wherein a first bias voltage provided to the first circuit and a second bias voltage provided to the second circuit are controlled independently of each other.

Some embodiments include apparatuses having a first path in a phase locked loop, the first path including a phase frequency detector to receive a first signal having a first frequency and a first node to provide a voltage; an oscillator coupled to a second node and the first node to provide a second signal having a second frequency at the second node; a second path including a frequency divider coupled to the second node and the phase frequency detector; and a circuit to generate digital information having a value based on a value of the voltage at the second node.

Some embodiments include apparatuses having a first path in a phase locked loop, the first path including a phase frequency detector to receive a first signal having a first frequency and a first node to provide a voltage; an oscillator coupled to a second node and the first node to provide a second signal having a second frequency at the second node; a second path including a frequency divider coupled to the second node and the phase frequency detector; and a circuit to generate digital information having a value based on a value of the voltage at the second node.

A frequency synthesizer includes a phase-locked loop (PLL). The PLL includes a first voltage-controlled oscillator (VCO) and a second VCO, each comprising an oscillator, a capacitor bank, and a bias circuit. The capacitor bank is configured to selectably adjust an output frequency of the oscillator. The bias circuit is configured to provide a bias current to the oscillator, and includes a current digital-to-analog converter (IDAC), and an amplifier coupled to the IDAC and configured to drive the oscillator.

Some embodiments include apparatuses having a first path in a phase locked loop, the first path including a phase frequency detector to receive a first signal having a first frequency and a first node to provide a voltage; an oscillator coupled to a second node and the first node to provide a second signal having a second frequency at the second node; a second path including a frequency divider coupled to the second node and the phase frequency detector; and a circuit to generate digital information having a value based on a value of the voltage at the second node.

Some embodiments include apparatuses having a first path in a phase locked loop, the first path including a phase frequency detector to receive a first signal having a first frequency and a first node to provide a voltage; an oscillator coupled to a second node and the first node to provide a second signal having a second frequency at the second node; a second path including a frequency divider coupled to the second node and the phase frequency detector; and a circuit to generate digital information having a value based on a value of the voltage at the second node.

A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.

A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.