Multi-Stop-Line TDC Architecture for Low-Latency Fine Time Resolution
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Solution Overview
Problem
Conventional time-to-digital converters (TDCs) face challenges in achieving low latency, good time resolution, and reduced power and area consumption while maintaining linearity, which are essential for advanced analog-to-digital conversion applications.
Innovation Solution
The proposed TDC architecture incorporates multiple stop lines with different delays and multiple sets of arbiters for comparing delayed signals, optimizing delay element configurations to reduce latency and power consumption while maintaining high resolution and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TDC architecture with single stop line is used, then device complexity is reduced, but time resolution and linearity deteriorate
Solution Approach 1:
The TDC is segmented into multiple independent delay lines (first delay line, second delay line, third delay line) each with different delay characteristics. This segmentation allows parallel measurement paths that improve time resolution while keeping each individual delay line relatively simple, thus resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The invention transitions from a single-stop-line architecture to a multi-dimensional architecture with multiple stop lines and multiple arbiter sets. By adding the dimension of multiple comparison paths, the system achieves superior time resolution and linearity without proportionally increasing overall complexity, as each dimension operates semi-independently.
2Speed
If flash ADC architecture is used, then conversion speed is improved, but power consumption and area increase exponentially
Solution Approach 1:
The conversion process is segmented into two independent stages: voltage-to-time conversion and time-to-digital conversion. This segmentation allows each stage to be optimized separately, achieving fast conversion speed without the exponential power and area cost of flash ADC, as the TDC portion uses efficient delay-line-based measurement rather than exhaustive parallel comparison.
Solution Approach 2:
The invention replaces the traditional voltage-based direct comparison mechanism with a time-based measurement mechanism. By converting voltage differences to time intervals and then measuring those intervals using delay lines and arbiters, the system achieves flash-ADC-speed conversion with significantly reduced power and area consumption.
3Measurement precision
If delay elements are increased to improve time resolution, then quantization latency increases
Solution Approach 1:
Different delay lines are designed with different local delay characteristics - the first delay line has a first delay time, the second delay line has a second delay time, and the third delay line has a third delay time. This local quality differentiation allows each delay line to be optimized for its specific function, achieving high time resolution without requiring any single delay line to be excessively long, thus reducing overall quantization latency.
Solution Approach 2:
The invention uses multiple delay lines with partial overlap in their delay ranges rather than requiring one extremely long delay line. By distributing the measurement function across multiple lines with different delay characteristics, the system achieves fine time resolution through combined measurement while each individual line maintains low latency.
Data Source
AI summary
Methods and apparatus for time-to-digital conversion. An example apparatus includes a first input; a second input; a delay line coupled to the first input and comprising a plurality of first delay elements coupled in series, each of the plurality of first delay elements having a first delay time; a second delay element having an input coupled to the second input and having the first delay time; a third delay element having an input coupled to the second input and having a second delay time, the second delay time being smaller than the first delay time; a first set of arbiters having first inputs coupled to the delay line and having second inputs coupled to an output of the second delay element; and a second set of arbiters having first inputs coupled to the delay line and having second inputs coupled to an output of the third delay element.