Digital calibration for multiphase oscillators
AssigneeRambus Inc.
InventorsMohammad Hekmat, Reza Navid
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Abstract
A phase-locked loop circuit comprises a multi-phase oscillator having a plurality of coupled oscillators. A calibration module detects mismatches between frequency characteristics of the different oscillators in the phase-locked loop circuit during a calibration process. The calibration module then calibrates the various oscillators to compensate for the detected mismatch. Once calibrated, the phase-locked loop circuit can operate with little or no performance degradation despite the mismatch in frequency characteristics between the different oscillators.
Claims20
A multi-phase oscillator circuit comprising:
- a first oscillator to receive a first compensated frequency control signal and to generate a first output signal having a frequency corresponding to a global frequency control signal and a first phase;
- a second oscillator to receive a second compensated frequency control signal and to generate a second output signal having the frequency corresponding to the global frequency control signal and a second phase different than the first phase;
- and
- a frequency compensation circuit to receive the global frequency control signal and to generate the first compensated frequency control signal for controlling the first oscillator and the second compensated frequency control signal for controlling the second oscillator based on detected variations in frequency characteristics between the first oscillator and the second oscillator.
A method for operating a multi-phase oscillator circuit comprising:
- receiving, by a frequency compensation circuit, a global frequency control signal;
- generating, by a frequency compensation circuit, a first compensated frequency control signal for controlling a first oscillator and a second compensated frequency control signal for controlling a second oscillator based on detected variations in frequency characteristics between the first and second oscillators;
- generating, by the first oscillator, a first output signal having a frequency corresponding to the global frequency control signal and a first phase;
- and
- generating, by the second oscillator, a second output signal having the frequency corresponding to the global frequency control signal and a second phase different than the first phase.
A method for calibrating a multi-phase oscillator circuit, the multi-phase oscillator circuit having a set of oscillators that when activated generate a plurality of output signals having a common frequency and different phases, the method comprising:
- monitoring operation of the multi-phase oscillator circuit in a first configuration in which a first oscillator in the set of oscillators is active and at least a second oscillator in the set of oscillators is inactive;
- monitoring operation of the multi-phase oscillator circuit in a second configuration in which the second oscillator is active and at least the first oscillator is inactive;
- detecting a mismatch between operation of the oscillators in the first configuration and the second configuration;
- and
- configuring an offset calibration component of at least one of the first oscillator and the second oscillator based on the mismatch.
Dependencies are inferred from the claim text.