Noise-Shaping SAR ADC for Multi-Input Sequential Conversion
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Solution Overview
Problem
Existing analog-to-digital (A/D) converters, specifically noise-shaping SAR A/D converters, are unable to efficiently convert multiple analog input voltages time-sequentially due to limitations in feedback mechanisms, resulting in increased conversion errors.
Innovation Solution
The proposed A/D converter incorporates an input switching circuit and a successive approximation register (SAR) A/D converting section, which includes a control unit, a D/A converting unit, a comparison reference voltage generating unit, and a comparator. This configuration allows for the selection and conversion of multiple analog input voltages time-sequentially, with the comparison reference voltage generating unit using integrated values from previous conversions to reduce error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a noise-shaping SAR A/D converter uses an integrating circuit to integrate residual voltages and feed them back for noise shaping, then noise is shifted to high-frequency band and resolution is improved, but the converter cannot process multiple analog input voltages time-sequentially
Solution Approach 1:
The patent divides the single integrating circuit into multiple integrating circuits, with each circuit dedicated to processing a specific analog input voltage. This segmentation allows each integrating circuit to maintain its noise-shaping function independently while enabling the system to process multiple input voltages time-sequentially by switching between the dedicated integrating circuits.
Solution Approach 2:
The patent creates a universal processing architecture where multiple integrating circuits share common functional blocks including the D/A converter, comparator, and control logic. This multi-functionality enables the system to handle multiple analog input voltages through time-sequential processing while maintaining the noise-shaping capability for each input channel.
2Adaptability or versatility
If the converter processes multiple analog input voltages time-sequentially without dedicated integrating circuits, then versatility is improved, but conversion error increases
Solution Approach 1:
The patent implements preliminary action by providing dedicated integrating circuits for each analog input voltage before the actual A/D conversion process. Each integrating circuit pre-processes its associated input voltage by integrating residual voltages and generating comparison reference voltages, ensuring that noise-shaping is already in effect before the voltage is selected for conversion, thereby reducing conversion error.
Solution Approach 2:
The patent employs feedback mechanisms in each integrating circuit where residual voltages from the D/A converter are fed back through the integrator to generate comparison reference voltages. This feedback loop maintains the noise-shaping function for each input channel, ensuring that conversion errors are minimized even when processing multiple voltages time-sequentially.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the A/D converter to efficiently convert multiple analog input voltages time-sequentially while minimizing conversion errors, achieving improved performance by utilizing integrated values as comparison reference voltages.
Implementation Method 1
The integrator integrates the differential voltage in a state where the A/D converting section has performed the conversion operation on the least significant bit
Implementation Method 2
The capacitor, connected to the output terminal of the integrator via the switching circuit, out of the plurality of capacitors is charged with an output voltage of the integrator
Data Source
AI summary
A comparator compares a differential voltage between a voltage to be converted as an analog input voltage and a comparative voltage generated by a D/A converting unit with a comparison reference voltage. A switching circuit selectively connects a capacitor, associated with the analog input voltage selected as the voltage to be converted, to an output terminal of an integrator. The integrator integrates the differential voltage in a state where an A/D converting section has performed conversion operation on a least significant bit. A comparison reference voltage generating unit uses, as the comparison reference voltage, a charge voltage for the capacitor associated with the analog input voltage selected as the voltage to be converted.