Injection-Locked Quadrature Clock Calibration for PVT Drift
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Solution Overview
Problem
Digital clock signals in integrated circuits experience undesired frequency drift due to process, voltage, and temperature variations, necessitating improved clock generation methods that minimize frequency drift.
Innovation Solution
A method for quadrature clock generation using injection locking with a digital calibration circuit comprising a coarse calibration circuit and a fine calibration circuit, which performs coarse frequency calibration, characterizes a replica oscillator signal path, and achieves fine frequency calibration by measuring phase differences between controlled and replica clock signals to generate calibrated quadrature clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free-running ring oscillator or injection-locked clock oscillator is used, then clock signal generation is achieved, but frequency drift occurs due to PVT variations
Solution Approach 1:
The calibration process is divided into two distinct segments: coarse frequency calibration and fine frequency calibration. The coarse calibration circuit performs initial frequency adjustment, while the fine calibration circuit performs subsequent precise adjustment. This segmentation allows each circuit to be optimized for its specific function, reducing overall complexity while achieving high frequency stability.
Solution Approach 2:
The coarse frequency calibration is performed before fine frequency calibration to pre-adjust the oscillator frequency close to the target value. This preliminary action reduces the calibration range required for the fine calibration circuit, simplifying its design and improving overall frequency accuracy.
2Reliability
If frequency calibration is performed to minimize drift, then frequency stability is improved, but calibration time and complexity increase
Solution Approach 1:
By dividing calibration into coarse and fine stages, the system achieves comprehensive frequency adjustment without requiring a single complex calibration process. The coarse calibration quickly brings the frequency close to target, while fine calibration makes precise adjustments, optimizing both accuracy and time efficiency.
Solution Approach 2:
The fine calibration circuit uses a phase detector to measure phase differences and adjusts the oscillator frequency with high precision. This partial action approach focuses calibration efforts on the critical frequency adjustment without performing unnecessary full-spectrum calibration, reducing overall calibration time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively minimizes frequency drift and generates stable quadrature clock signals, addressing the challenges of frequency offset and drift in digital clock generation.
Implementation Method 1
a free-running ring oscillator or an injection-locked clock oscillator may have undesired frequency drift due to process, voltage and temperature (PVT) variations in the integrated circuit
Data Source
AI summary
Aspects of the disclosure are directed to quadrature clock generation with injection locking. In accordance with one aspect, quadrature clock generation with injection locking uses a digital calibration circuit having a coarse calibration circuit and a fine calibration circuit to perform a coarse frequency calibration of a controlled oscillator, wherein the controlled oscillator is coupled to the digital calibration circuit; characterize a replica oscillator signal path associated with an oscillator replica circuit, wherein the oscillator replica circuit is coupled to the controlled oscillator; perform a fine frequency calibration of the controlled oscillator by measuring a phase difference between the controlled oscillator and the oscillator replica circuit; and generate a calibrated set of quadrature clock signals after performing the fine frequency calibration of the controlled oscillator.