High-Gain PLL Phase Detector With Supply Noise Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High gain phase detector techniques for phase-locked loops (PLLs) are sensitive to process and temperature variations, supply noise, and limited supply voltage, which degrades PLL jitter performance and phase noise at low frequency offsets.
Innovation Solution
A PLL analog loop filter structure with a passive feedforward path and a lossy integrating path using opamp circuits with both inverting and non-inverting gains to reduce supply noise, combined with a digital-to-time converter to minimize quantization errors, and charge pump techniques to enhance PD gain and reduce sensitivity to supply noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high gain phase detector techniques are used, then phase noise performance is improved, but sensitivity to supply noise increases
Solution Approach 1:
The phase detector is divided into two separate detectors with opposite gain polarity, allowing the useful phase detection function to be doubled while the supply noise components cancel each other out through differential combination
Solution Approach 2:
The supply noise that normally degrades performance is converted into a beneficial cancellation mechanism where identical noise components from two detectors subtract from each other, transforming a harmful factor into a noise rejection mechanism
2Power
If slope-based sampling PD structure is used, then gain is improved, but process and temperature sensitivity increases
Solution Approach 1:
The single slope-based detector is segmented into two detectors with opposite polarity, where the differential combination cancels out PT-sensitive variations while preserving the high gain characteristic
Solution Approach 2:
The gain polarity parameter is inverted for the second detector, creating a differential configuration that changes the system's response to PT variations from additive to subtractive, thereby improving stability
3Stability of the object's composition
If Up/Down RC charging circuits are used, then robustness against PT variation is improved, but supply voltage limitation increases
Solution Approach 1:
The Up/Down RC charging circuits are merged with slope-based detectors in a hybrid configuration, combining the PT robustness of RC circuits with the high gain of slope-based detection while managing supply voltage requirements
4Measurement precision
If high gain phase detector is used, then phase noise at low frequency offsets is improved, but detector noise impact increases
Solution Approach 1:
The detector is segmented into two independent detectors whose noise components are uncorrelated, allowing the useful signal to add constructively while noise components cancel partially through differential combination
Solution Approach 2:
The gain polarity parameter is changed for the second detector, creating a differential configuration where the phase detection response adds while detector noise components subtract, reducing overall noise impact
Data Source
AI summary
In described examples, a phase measurement circuit includes a first switch coupled between a power terminal and a phase measurement output, the first switch having a first switch control terminal coupled to an up input. The phase measurement circuit includes a second switch coupled between the phase measurement output, the second switch having a second switch control terminal coupled to a down input. The phase measurement circuit includes a first capacitor coupled between the power terminal and the phase measurement output, a second capacitor coupled between the phase measurement output and a ground terminal, and a charge pump circuit having a first control input, a second control input, and a charge pump output, the first control input coupled to the up input, the second control input coupled to the down input, and the charge pump output coupled to the phase measurement output.