Mixed-Signal TDC with Embedded T2V ADC for Precise PLL Phase Locking
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Solution Overview
Problem
Existing time-to-digital converters face challenges in accurately converting the difference between transition times of a reference clock signal and an oscillating signal to a digital signal, particularly in phase-locked loops, where precise phase locking is required but noise filtering and high frequency component management are complex.
Innovation Solution
A time-to-digital converter comprising an edge detector, a time-to-voltage converter, and an analog-to-digital converter, where differential outputs are charged or discharged based on the relative arrival times of signal edges, with transistors and capacitors used to generate an analog signal proportional to the timing difference, and a successive approximation register ADC for digitization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional time-to-digital converters are used to convert timing differences to digital signals in phase-locked loops, then phase locking can be achieved, but measurement precision and noise filtering become complex
Solution Approach 1:
The converter is divided into three functional segments: edge detector circuitry for detecting signal transitions, time-to-voltage converter circuitry for converting time differences to voltage signals, and analog-to-digital converter circuitry for digitizing the voltage signals. This segmentation simplifies noise filtering by allowing each segment to be optimized independently for its specific function.
Solution Approach 2:
The patent introduces an intermediary time-to-voltage conversion stage between the edge detection and analog-to-digital conversion processes. This intermediary converts the time difference into a voltage signal that can be more easily filtered and processed, reducing the complexity of direct time-to-digital conversion while maintaining measurement precision.
2Measurement precision
If the time-to-digital converter uses differential outputs charged to predefined voltage levels, then the conversion accuracy is improved, but the circuit complexity increases due to multiple transistors and capacitors
Solution Approach 1:
The differential output circuit uses transistors and capacitors that serve multiple functions: the transistors act as switches for charging/discharging the capacitors to predefined voltage levels, while also functioning as amplifiers and signal conditioners. This multi-functionality reduces the need for additional dedicated components, thereby improving precision without proportionally increasing complexity.
3Productivity
If edge detection is performed during each period of the reference clock signal, then the conversion speed is improved, but the reliability may be affected by noise and signal variations
Solution Approach 1:
The edge detector circuitry incorporates feedback mechanisms that monitor the detected edges and adjust its operation to maintain accuracy despite noise and signal variations. The feedback ensures that only valid edges are detected and processed, improving reliability while maintaining the high conversion rate achieved by operating during each clock period.
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 solution effectively converts timing differences into digital signals, enhancing phase locking precision and noise filtering in phase-locked loops, thereby improving the accuracy and reliability of phase synchronization.
Implementation Method 1
The time-to-voltage converter is adapted to generate an analog signal having a value proportional to the difference between the occurrences of the detected edge of the oscillating signal and the edge of the reference clock signal
Implementation Method 2
the time-to-digital converter has first and second differential outputs that are charged to a predefined voltage level in response to a reset signal
Implementation Method 3
a conductive path is formed between the first differential output and a first supply voltage via first and second transistors if the edge of the reference clock signal leads the detected edge of the oscillating signal
Implementation Method 4
The analog-to-digital converter is adapted to convert the analog signal to a digital signal
Data Source
AI summary
A time-to-digital converter converts the difference between transition times of a reference clock signal and an oscillating signal to a digital signal whose value is proportional to the transitions timing difference. The time-to-digital converter includes an edge detector, a time-to-voltage converter, and an analog-to-digital converter. The edge detector is adapted to detect, during each period of the reference clock signal, the edge (transition) of the oscillating signal that is closest to the edge of the reference clock signal. The time-to-voltage converter is adapted to generate an analog signal proportional to a difference in time between the detected edge of the oscillating signal and the edge of the reference clock signal. The analog-to-digital converter is adapted to convert the analog signal to a digital signal whose value is proportional the difference between the occurrence of the detected edge of the oscillating signal and the edge of the reference clock signal.