Movellus Circuits Inc.

Frederick Christopher Candler

Jeffrey Alan Fredenburg

A locked-loop circuit includes phase synchronization circuitry to synchronize a DCO clock phase to a reference clock phase. Sampling circuitry sequentially samples the reference clock with each of N sampling clocks having offset phases, a first one of the N sampling clocks comprising a master sampling clock. Edge detection logic accumulates phase information from the multiple sampling clocks and determines, based on the accumulated phase information, whether any of the sampling clocks other than the master sampling clock correspond to edge detection signals that occurred early with respect to a rising edge of the master sampling clock. Index logic generates index values for any of the determined early edge detection signals. The index logic transfers the generated index values to a master phase transfer logic unit. Phase adjust logic adjusts the master clock phase based on a selected one of the generated index values.

Locked loop circuit and method with multi-phase synchronization

A method of operation in a locked-loop circuit. The locked-loop circuit includes a loop filter and a digitally-controlled oscillator (DCO). The loop filter includes a first input to receive a digital word representing a difference between a reference clock frequency and a DCO output frequency. The loop filter includes internal storage. The method includes selecting a desired DCO output frequency that is generated in response to a calibration DCO codeword. A start value is retrieved from the loop filter internal storage. The start value corresponds to the calibration DCO codeword. The locked-loop circuit is then started with the retrieved start value.

Locked loop circuit and method with digitally-controlled oscillator (DCO) gain normalization

A method of operation in a locked-loop circuit. The locked-loop circuit includes a loop filter and a digitally-controlled oscillator (DCO) coupled to the output of the loop filter. The loop filter includes a first input to receive a digital word representing a difference between a reference clock frequency and a DCO output frequency. The method includes determining a calibration DCO codeword representing a calibration operating point for the locked-loop circuit; determining a scaling factor based on the calibration operating point, the scaling factor based on a ratio of an actual DCO gain to a nominal DCO gain; and applying the scaling factor to operating parameters of the loop filter.

A locked-loop circuit includes a time-to-digital converter (TDC) having a reference clock input and an error input. A digital loop filter receives an output from the TDC representing a difference between the reference clock input and the error input. A digitally-controlled oscillator (DCO) receives an output from the digital filter in the form of output bits. The DCO has a codeword gain associated with a DCO control word. The codeword gain is applied to the output bits received from the digital loop filter. Calibration logic determines a scaling factor based on a process-voltage-temperature (PVT) operating characteristic. The scaling factor is applied to normalize an actual DCO codeword gain to the codeword gain. The DCO includes an output to deliver an output timing signal having a frequency based on the scaling factor.

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Frederick Christopher Candler