Apple Inc.

Cristian Marcu

Feng Zhao

Simone Gambini

Wei Deng

Long Kong

Robert K Kong

Nachum M Kanovsky

Saeed Chehrazi

Chunwei Chang

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.

Voltage-controlled oscillator calibration

In a computer system, a phase-locked loop circuit may generate a clock signal using a reference signal. The phase-locked loop circuit may include a programmable divider stage that includes multiple divider stages. When a frequency calibration is initiated on the phase-locked loop circuit, a control circuit may generate a pause signal in response to one or more of the divider stages reaching a particular logic state. The programmable divider stage may hold the one or more of the divider stages in the particular logic state using the pause signal.

Divider control and reset for phase-locked loops

An oscillator subsystem included in a phase-locked loop circuit of a computer system may include coarse and fine-tuning circuits. The coarse-tuning circuit may generate a coarse-tuning current based on a reference voltage, and the fine-tuning circuit may generate a fine-tuning current by combining respective currents generated by first and second complement current mirror circuits using a voltage level of a control signal. An oscillator circuit may generate a clock signal whose frequency is based on a combination of the coarse and fine-tuning circuits.

Voltage-to-current converter circuit

Growing community of inventors

San Jose, CA, United States of America

Cristian Marcu