Hybrid ADC Architecture for Low-Power Accurate Temperature Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for a low-power, accurate analog-to-digital converter (ADC) that is compatible with temperature sensing in non-contact transponders, as existing ADCs often consume high power and lack the necessary accuracy for precise temperature measurements.
Innovation Solution
The proposed ADC combines a direct comparison converter for a fast, initial approximation with a sigma-delta converter for precise digital output, utilizing a first-order sigma-delta modulator to minimize power consumption and achieve high resolution, and incorporates dynamic error correction and element matching for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sigma-delta ADC is used to provide high resolution, then measurement precision is improved, but use of energy increases and conversion time increases exponentially
Solution Approach 1:
The ADC conversion process is segmented into two distinct stages: a coarse conversion stage that provides initial approximation and a fine conversion stage that refines the result. This segmentation allows the system to achieve high resolution without requiring a single high-power sigma-delta converter to complete the entire conversion, thereby reducing overall power consumption while maintaining measurement precision.
Solution Approach 2:
The coarse conversion stage performs preliminary action by providing an initial approximation of the analog input voltage before the fine conversion stage. This preliminary digital value narrows the range for subsequent precise measurement, allowing the fine conversion stage to operate more efficiently with reduced power requirements while achieving the final high-resolution result.
2Measurement precision
If a sigma-delta ADC is used to provide high resolution, then measurement precision is improved, but conversion time increases exponentially
Solution Approach 1:
The conversion process is divided into coarse and fine stages, each with optimized conversion times. The coarse stage quickly establishes the initial digital value, and the fine stage subsequently refines this value. This segmentation prevents the exponential conversion time increase associated with single-stage high-resolution sigma-delta converters, achieving both speed and precision.
Solution Approach 2:
The coarse conversion stage performs preliminary action by rapidly establishing an initial approximation of the analog input. This preliminary digital value significantly reduces the remaining voltage range that the fine conversion stage must resolve, thereby dramatically reducing the total conversion time required to achieve high resolution compared to a single-stage approach.
3Productivity
If a direct comparison converter is used for fast conversion, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The converter is segmented into two functional stages: a direct comparison converter for coarse conversion that prioritizes speed, and a sigma-delta converter for fine conversion that prioritizes precision. This segmentation allows each stage to be optimized for its specific function, achieving both fast conversion and high resolution that neither stage could achieve alone.
Solution Approach 2:
The invention merges two different ADC architectures (direct comparison and sigma-delta) into a unified hybrid system. The coarse converter and fine converter are combined such that the output of one feeds into the other, creating a synergistic system that achieves both the speed of direct comparison conversion and the precision of sigma-delta conversion.
Data Source
AI summary
An ADC is disclosed which has, as a first stage, a successive approximation converter, or other compensated, direct comparison converter, followed by a sigma delta modulation converter as a second stage. The sigma delta converter may beneficially be a first order modulator. The resulting ADC combines accuracy with low power consumption per conversion, and thus is particularly suited for use in temperature sensors for applications such as RFID transponders. Such a temperature sensor and an RFID transponder are also disclosed. There is also disclosed a method of analog-to-digital conversion, comprising a first successive approximation register or other compensated, direct comparison conversion stage followed by a sigma delta modulation stage, which, further, may be combined with providing a proportional-to-absolute-temperature (PTAT) signal, for low-power, accurate temperature sensing.