SAR ADC Comparator Architecture for Lower Feedback Loop Delay
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Solution Overview
Problem
The sampling speed of successive-approximation analog-to-digital converters (SAR ADCs) is limited by the feedback loop comprising the comparator, digital-to-analog converter (DAC), and SAR logic, leading to delays and power consumption issues, with existing techniques increasing hardware complexity and power dissipation.
Innovation Solution
The implementation of a regeneration-unrolled comparator (RUC) with a single integration circuit and multiple regeneration circuits, which stores decision bits directly, allowing the DAC to be controlled by comparison results, reducing the feedback loop delay and eliminating the need for memory cells and additional logic, thereby enhancing sampling speed and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a regenerative comparator with integration and regeneration stages is used, then comparison accuracy is improved, but feedback loop delay increases
Solution Approach 1:
The comparator is divided into multiple independent regeneration circuits (first, second, third regeneration circuits) that operate in parallel. Each circuit processes a specific portion of the comparison task, allowing simultaneous operation and reducing the overall feedback loop delay while maintaining comparison accuracy through distributed regeneration stages.
Solution Approach 2:
The first regeneration circuit performs preliminary regeneration of the comparison result before it is passed to subsequent circuits. This preliminary action prepares the signal in advance, reducing the processing time required by later stages and thereby decreasing the total feedback loop delay.
2Productivity
If multiple regeneration circuits are used to reduce feedback loop delay, then sampling speed is improved, but power consumption increases
Solution Approach 1:
The regeneration circuits are controlled dynamically through control signals that enable or disable specific circuits based on the conversion stage. Not all regeneration circuits operate simultaneously or continuously; instead, they are activated only when needed, allowing the system to achieve high sampling speed when required while reducing power consumption during idle or less demanding periods.
Solution Approach 2:
The regeneration circuits automatically activate and deactivate based on the state of the conversion process and control signals from the digital-to-analog converter. The system self-regulates its operation without requiring external continuous control, optimizing the balance between sampling speed and power consumption autonomously.
3Reliability
If traditional SAR logic with memory cells is used, then decision bit storage is achieved, but hardware complexity increases
Solution Approach 1:
The storage function traditionally performed by separate memory cells and SAR logic is merged into the regeneration circuits themselves. The regeneration circuits inherently store the decision bits through their regenerative nature, eliminating the need for dedicated memory cells and reducing hardware complexity while maintaining reliable decision bit storage.
Solution Approach 2:
The regeneration circuits serve multiple functions: they perform signal regeneration, store decision bits, and provide feedback control. This multi-functionality replaces the need for separate dedicated components for each function, reducing overall hardware complexity while maintaining the required reliability for decision bit storage.
Data Source
AI summary
A successive-approximation analog-to-digital converter includes a sampling circuit for sampling an analog input signal to acquire a sampled voltage, and a regenerative comparator for comparing the sampled voltage with a succession of reference voltages to generate, for each reference voltage, a decision bit indicating the comparison result. The converter also includes a digital-to-analog converter which is adapted to generate the succession of reference voltages, in dependence on successive comparison results in the comparator, to progressively approximate the sampled voltage. The regenerative comparator comprises an integration circuit for generating output signals defining the decision bits, and a plurality of regeneration circuits for receiving these output signals. The regeneration circuits are operable, in response to respective control signals, to store respective decision bits defined by successive output signals from the integration circuit.