Recirculating Delay Line Gain Stage for Higher-Resolution TDCs
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Solution Overview
Problem
Time-to-Digital Converters (TDCs) face limitations in resolution due to native resolution constraints, which affect accuracy and stability, particularly in phase-locked loops, where traditional methods either provide high stability with poor resolution or high resolution with poor accuracy, and are sensitive to process, voltage, and temperature variations.
Innovation Solution
The introduction of a gain stage using a time amplifier with a delay line to recirculate time information, providing a known fixed PVT-invariant gain, improves the effective resolution of TDCs by repetitive addition of input pulses to an integrating time-to-digital converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high frequency system clock is used to improve resolution, then the resolution improves, but power dissipation increases
Solution Approach 1:
A recirculating delay line is introduced as an intermediary mechanism between the input pulse and the TDC. The delay line recirculates the input pulse multiple times, allowing the TDC to integrate multiple copies of the same pulse without requiring a higher frequency clock. This mediator enables high resolution measurement while maintaining lower power consumption.
Solution Approach 2:
The delay line creates periodic recirculation of the input pulse through feedback routing. Instead of using a continuous high-frequency clock, the system uses periodic recirculation where the pulse traverses the delay line multiple times at a lower frequency, accumulating measurement precision over multiple passes without the continuous power demand of a high-frequency clock.
2Measurement precision
If gate delay time base is used to improve resolution, then resolution improves, but accuracy deteriorates due to PVT variations
Solution Approach 1:
The delay line creates multiple copies of the input pulse through recirculation. Each circulation generates an additional pulse that is fed to the integrating TDC. This copying mechanism allows the system to achieve high resolution by counting multiple identical pulse copies rather than relying on a single high-precision but PVT-sensitive gate delay measurement.
Solution Approach 2:
The periodic recirculation of pulses through the delay line enables the system to perform multiple measurements of the same input signal under varying conditions. By integrating multiple periodic pulse arrivals, the system averages out PVT variations and achieves both high resolution and improved accuracy.
3Stability of the object's composition
If traditional voltage mode phase storage is used, then stability is achieved, but resolution is poor
Solution Approach 1:
The patent replaces the traditional voltage-mode capacitive storage mechanism with a time-domain pulse recirculation system. Instead of storing phase information as voltage on a capacitor (which has inherent resolution limits), the system stores and processes phase information as recirculating time pulses, enabling higher resolution measurement while maintaining stability through the deterministic nature of digital pulse propagation.
Data Source
AI summary
The resolution of a time to digital converter (TDC) is improved by using a gain stage at the input of the fine TDC. A delay line receives a pulse corresponding to the time information and recirculates the pulse in the delay line by coupling an output of the delay line to an input of the delay line. An integrating fine TDC receives a number of pulses from the delay line corresponding to the desired gain.