Multichannel SAR ADC Layout With Shared DAC for Low-Noise Conversion
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Solution Overview
Problem
Existing multichannel successive approximation analog-to-digital converters (SA-ADCs) are expensive and inefficient when converting multiple analog signals simultaneously, as they require multiple converters or large capacitors, which occupy significant space and introduce noise.
Innovation Solution
A successive approximation analog-to-digital converter design that uses a single digital-to-analog converter with multiple first conversion units and a single second conversion unit, employing capacitor arrays and switch arrays controlled by a control circuit to sample and compare analog signals efficiently, allowing simultaneous conversion of multiple signals while minimizing noise and space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple SA-ADCs are used to convert multiple analog signals simultaneously, then conversion capability is improved, but cost and device complexity increase significantly
Solution Approach 1:
Multiple first conversion units are merged into a single digital-to-analog converter structure, sharing common components including the second conversion unit, capacitor arrays, switch arrays, comparator, and control logic. This merging enables simultaneous conversion of multiple analog signals while reducing the total number of discrete converters needed.
Solution Approach 2:
The single digital-to-analog converter structure performs multiple functions by processing several analog signals simultaneously through its multiple first conversion units. The shared second conversion unit and control circuitry serve all channels, making the device universal rather than requiring dedicated converters for each signal.
2Productivity
If traditional multichannel SA-ADC designs are used, then simultaneous signal conversion is achieved, but surface area and space requirements increase
Solution Approach 1:
The design merges multiple conversion functions into a single integrated structure where first conversion units share common second conversion unit, capacitor arrays, switch arrays, and control circuitry. This consolidation significantly reduces the surface area compared to using separate converters for each channel.
Solution Approach 2:
The patent organizes conversion units in a multi-dimensional array structure with first conversion units arranged to share resources in systematic ways. This spatial organization optimizes the use of available surface area while maintaining simultaneous conversion capability across multiple channels.
3Productivity
If multiple converters are used for multichannel conversion, then conversion capability is improved, but noise increases
Solution Approach 1:
By merging multiple first conversion units into a single digital-to-analog converter structure with shared second conversion unit and common reference signals, the design reduces the total number of independent noise-generating components. Fewer separate converters mean fewer independent noise sources, thereby reducing overall noise while maintaining multichannel conversion capability.
4Device complexity
If a single SA-ADC converts signals successively, then device complexity is reduced, but conversion efficiency decreases
Solution Approach 1:
The control circuit dynamically controls the switch arrays to enable simultaneous operation of multiple first conversion units while using a single second conversion unit. This dynamic time-multiplexed approach allows the single converter structure to process multiple analog signals in parallel, achieving high conversion efficiency without requiring multiple physical converters.
Solution Approach 2:
The control circuit employs periodic switching patterns to systematically allocate the second conversion unit and shared resources among multiple first conversion units. This periodic action enables efficient resource utilization and maintains high conversion throughput while using a single converter structure.
Data Source
AI summary
A successive approximation analog-to-digital converter includes a digital-to-analog converter DAC configured to receive a digital signal. First conversion units of the DAC are configured to sample an analog signal via a first switch and provide a first level voltage. Each first conversion unit includes a first capacitor array and a first switch array controlled from the digital signal. A single second conversion unit of the DAC is configured to provide a second level voltage. The second conversion unit includes a second capacitor array and a second switch array. A comparator operates to compare each of the first level voltages to the second level voltage and to provide a comparison signal based on each comparison and actuation of a set of third switches. A control circuit closes the first switches simultaneously and closes the third switches successively for the conversion of each sampled analog signal.