Capacitive ADC Reference Switching to Reduce Dielectric Relaxation Error
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Solution Overview
Problem
Analog-to-digital conversion circuits experience significant conversion errors due to the dielectric relaxation phenomenon when processing multiple analog input signals in a time division manner, particularly when switching between signals, leading to variations in input voltage and increased error rates.
Innovation Solution
The implementation of a dual digital-to-analog conversion circuit system, where a first capacitance distribution type and a second capacitance distribution type are used in conjunction with a comparison circuit to generate an intermediate digital value, allowing for a successive comparison operation with adjusted reference voltages, thereby reducing conversion errors caused by dielectric relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple analog input signals are processed in a time division manner with switching, then the conversion speed and processing capability are improved, but the conversion error increases due to dielectric relaxation phenomenon
Solution Approach 1:
The patent applies preliminary action by performing a first analog-to-digital conversion before the main successive comparison operation. This preliminary conversion provides an initial digital value that is used to set the reference voltage for the second digital-to-analog conversion circuit, preparing the system in advance to compensate for dielectric relaxation effects during the main conversion process.
Solution Approach 2:
The patent implements feedback by using the output of the first analog-to-digital conversion circuit to control the reference voltage of the second digital-to-analog conversion circuit. The intermediate digital value from the first conversion feeds back into the system to adjust and compensate for errors in the main conversion process, thereby reducing the overall conversion error.
2Measurement precision
If the reference voltage is switched to improve CMRR and PSRR, then the conversion accuracy is improved, but the complexity of the circuit increases
Solution Approach 1:
The patent divides the conversion process into two separate conversion circuits (first and second analog-to-digital conversion circuits) with different functions. The first circuit performs a preliminary conversion to generate an intermediate digital value, while the second circuit performs the main successive comparison operation. This segmentation allows each circuit to be optimized for its specific purpose, improving overall accuracy without requiring a single overly complex circuit.
Solution Approach 2:
The patent introduces an intermediate digital value as a mediator between the preliminary conversion and the main conversion process. This intermediate value serves as a control signal that adjusts the reference voltage of the second digital-to-analog conversion circuit, enabling error compensation without requiring direct complex interconnections between all circuit components.
3Device complexity
If a single-ended input is used for analog-to-digital conversion, then the circuit simplicity is improved, but the conversion error due to dielectric relaxation increases
Solution Approach 1:
The patent applies preliminary action by performing a first analog-to-digital conversion before the main successive comparison operation. This preliminary conversion provides an initial digital value that is used to set the reference voltage for the second digital-to-analog conversion circuit, preparing the system in advance to compensate for dielectric relaxation effects during the main conversion process.
Solution Approach 2:
The patent changes the parameter of reference voltage dynamically based on the intermediate digital value from the first conversion. By adjusting the reference voltage parameter of the second digital-to-analog conversion circuit according to the preliminary conversion result, the system compensates for dielectric relaxation effects while maintaining the simplicity of the single-ended input structure.
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
This approach effectively minimizes conversion errors by stabilizing the charge distribution across capacitors, ensuring accurate digital conversion even when switching between multiple analog input signals, thereby enhancing the resolution and reliability of the analog-to-digital conversion process.
Implementation Method 1
a first digital-to-analog conversion circuit of a capacitance distribution type, a second digital-to-analog conversion circuit of a capacitance distribution type
Implementation Method 2
a comparison circuit for comparing output voltages of the two digital-to-analog conversion circuits
Data Source
AI summary
A conventional analog-to-digital conversion circuit has a problem that conversion errors cannot be suppressed. According to one embodiment, the analog-to-digital conversion circuit includes a first digital-to-analog conversion circuit 30 of a capacitance distribution type, a second digital-to-analog conversion circuit 31 of a capacitance distribution type, and a comparison circuit 32 for comparing output voltages of the two digital-to-analog conversion circuits, and before performing a successive comparison operation for successively changing a reference voltage applied to the first digital-to-analog conversion circuit, generates an intermediate digital value having a digital value corresponding to a voltage value of an analog input signal, determines a reference voltage to be applied to the second digital-to-analog conversion circuit 31 in accordance with the intermediate digital value, and thereafter performs a successive comparison operation using the first digital-to-analog conversion circuit 30 in a state in which the state of the second digital-to-analog conversion circuit 31 is held.