Dual-Clock Time-to-Digital Conversion for Jitter-Accurate Timing
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Solution Overview
Problem
Existing time-to-digital converters face challenges in achieving high accuracy due to factors like temperature characteristics, process variations, and jitter in oscillator signals, which affect the measurement of time differences between arbitrary signal timings.
Innovation Solution
A time-to-digital converter design utilizing two reference clock signals with different frequencies, generated using oscillators with excellent characteristics such as quartz crystal resonators, to convert time differences into digital values with increased resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a ring oscillator is used to generate clock signals, then the device complexity is reduced and ease of manufacture is improved, but the measurement precision deteriorates due to temperature characteristics, process variation, and jitter
Solution Approach 1:
A delay circuit is introduced as an intermediary component between the ring oscillator and the measurement system. This delay circuit compensates for variations in clock signal timing caused by temperature, process variation, and jitter, thereby maintaining measurement precision while allowing the use of simple ring oscillators.
Solution Approach 2:
The invention adjusts and optimizes parameters of the ring oscillator and delay circuit to minimize the impact of temperature characteristics and process variation. By carefully controlling oscillation frequency, delay time, and circuit timing parameters, the system achieves acceptable measurement precision without requiring complex oscillators.
2Measurement precision
If a quartz crystal oscillator is used to improve oscillation characteristics, then the measurement precision is improved, but the ease of operation deteriorates because it is difficult to control the start of oscillation at the transition timing of signals
Solution Approach 1:
The invention replaces the mechanical/physical quartz crystal oscillator with an electronic ring oscillator system enhanced by a delay circuit. This substitution maintains measurement precision through electronic compensation while eliminating the operational complexity of controlling quartz crystal start timing.
Solution Approach 2:
The delay circuit performs preliminary timing adjustment and compensation before the actual measurement process. By pre-correcting for expected variations in clock signal timing, the system ensures accurate measurements without requiring precise manual control of oscillator start timing.
3Device complexity
If one clock signal is used for time measurement, then the device complexity is reduced, but the measurement precision deteriorates due to waveform generation accuracy and distortion
Solution Approach 1:
The time measurement function is segmented into multiple independent components: a first clock signal path for measuring the time of the first signal, and a second clock signal path for measuring the time of the second signal. Each path uses its own clock signal and measurement circuitry, which eliminates errors caused by waveform distortion in a single shared clock signal while keeping overall device complexity manageable through modular design.
Data Source
AI summary
A time-to-digital converter includes a clock signal generation circuit that generates a first cycle signal having a voltage level that monotonously increases or decreases in a cycle corresponding to the clock frequency of a reference clock signal and further generates a first clock signal based on a first signal and the first cycle signal, a clock signal generation circuit that generates a second cycle signal having a voltage level that monotonously increases or decreases in a cycle corresponding to the clock frequency of a reference clock signal and further generates a second clock signal based on a second signal and the second cycle signal, and a processing circuit that converts a time difference between the transition timing of the first signal and the transition timing of the second signal into a digital value based on the first and second clock signals.