Hybrid Coarse-Fine Time-to-Digital Conversion for Low Offset
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Solution Overview
Problem
Existing time-to-digital converters face challenges in achieving a balance between fine quantization resolution, low offset, and good linearity, as coarse converters have small offset and better linearity but large quantization resolution, while fine converters have smaller noise but larger offset and worse linearity, making them sensitive to process, voltage, and temperature variations.
Innovation Solution
A hybrid coarse-fine time-to-digital converter is designed, comprising a coarse time-to-digital converter, a fine time-to-digital converter, and a correlated output generator, which generates intermediate outputs that are correlated to produce a digital output with finer resolution and reduced offset, using a time amplifier and bi-directional time-to-digital converter to improve quantization resolution and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fine time-to-digital converter is used to achieve finer quantization resolution, then quantization noise is reduced, but offset increases and linearity deteriorates
Solution Approach 1:
The converter is divided into two independent sub-converters: a coarse time-to-digital converter and a fine time-to-digital converter. Each sub-converter is optimized for its specific function - the coarse converter handles offset and linearity while the fine converter provides high resolution. Their outputs are then combined through correlation to achieve both high resolution and good linearity simultaneously.
2Reliability
If a coarse time-to-digital converter is used to achieve small offset and better linearity, then reliability improves, but quantization resolution becomes much larger
Solution Approach 1:
The outputs of the coarse and fine time-to-digital converters are merged through a correlation operation. The coarse converter output provides the baseline with good linearity, while the fine converter output adds the high-resolution detail. The correlation combines these two outputs to produce a final digital output that inherits the advantages of both converters.
3Measurement precision
If fine time-to-digital converter is used to reduce quantization noise, then measurement precision improves, but sensitivity to process, voltage, and temperature variations increases
Solution Approach 1:
The coarse time-to-digital converter acts as an intermediary that processes the time difference signal before it reaches the fine converter. By having the coarse converter handle the initial time difference measurement and provide a stabilized reference, the fine converter operates on a more stable input, reducing its sensitivity to PVT variations while maintaining high resolution.
Data Source
AI summary
A hybrid coarse-fine time-to-digital converter is disclosed. The hybrid coarse-fine time-to-digital converter is configured to receive a first input signal and a second input signal and to generate a digital output that corresponds to the time difference of between a rising edge of the first input signal and a rising edge of the second input signal. The hybrid coarse-fine time-to-digital converter comprises a coarse time-to-digital converter, a fine time-to-digital converter, and a correlated output generator.