Charge-Injection SAR ADC Calibration for Linearity Without Extra DACs
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Solution Overview
Problem
Existing successive approximation register analog to digital converters face increased circuit area and cost due to the need for additional digital to analog converters to compensate for mismatches in current source circuits, which affects the accuracy and linearity of the conversion process.
Innovation Solution
A successive approximation register analog to digital converter utilizing a charge injection digital to analog converter circuit with capacitors and charge injection circuits, along with a comparator and control logic circuitry, which adjusts the switching sequence of the charge injection circuits to improve linearity and reduce mismatches without requiring additional digital to analog converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional digital to analog converters are employed to calibrate current source circuits, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the calibration function from a separate additional digital-to-analog converter and integrates it into the existing charge injection digital-to-analog converter circuit. By taking out the calibration operation as a distinct phase (initial phase) within the conversion process, the system achieves accurate calibration without requiring separate calibration hardware, thus improving measurement precision while avoiding increased device complexity.
Solution Approach 2:
The patent applies preliminary action by performing calibration operations during an initial phase before the main analog-to-digital conversion. The control logic circuitry pre-adjusts the charge injection circuits to compensate for mismatches in current source circuits during this initial phase, ensuring accurate conversion results for subsequent operations without requiring additional calibration hardware.
2Manufacturing precision
If additional digital to analog converters are employed to calibrate current source circuits, then manufacturing precision is improved, but area of stationary object increases
Solution Approach 1:
The charge injection digital-to-analog converter circuit is designed to serve multiple functions: it performs both the main analog-to-digital conversion and the calibration of current source circuits. By making the charge injection circuit universal, the system achieves improved manufacturing precision (linearity) without requiring additional dedicated calibration converters, thus avoiding increase in circuit area.
Solution Approach 2:
The patent merges the calibration function with the existing charge injection digital-to-analog converter circuit. Instead of having separate calibration and conversion circuits, the system combines both functions into a single integrated circuit structure, achieving accurate linearity calibration while minimizing the overall circuit area occupied.
3Measurement precision
If additional digital to analog converters are employed to calibrate current source circuits, then measurement precision is improved, but cost increases
Solution Approach 1:
The charge injection digital-to-analog converter circuit performs self-calibration by using its own structure to compensate for mismatches in current source circuits. The control logic circuitry automatically adjusts the charge injection circuits during an initial phase without requiring external calibration equipment or additional calibration converters, achieving improved measurement precision while reducing device cost through self-service calibration.
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 enhances the linearity and resolution of the digital output by calibrating the charge injection digital to analog converter circuit, reducing the impact of mismatches and maintaining accuracy without significantly increasing the circuit area or device cost.
Implementation Method 1
a plurality of capacitors are configured to respectively sample a plurality of input signals to generate a first signal and a second signal
Implementation Method 2
a plurality of charge injection circuits are configured to selectively adjust at least one of the first signal or the second signal according to a plurality of enable signals and a plurality of decision signals
Data Source
AI summary
A successive approximation register analog to digital converter includes a charge injection digital to analog converter (DAC) circuit, a comparator circuit, and a control logic circuitry. The charge injection DAC circuit includes capacitors that sample input signals to generate first and second signals and charge injection circuits that selectively adjust the first or the second signals according to enable signals and decision signals. The comparator circuit compares the first and second signals to generate the decision signals. The control logic circuitry controls a circuit of the charge injection circuits to adjust the first and the second signals during an initial phase, in order to adjust a switching sequence of the circuit according to the decision signals corresponding to the initial phase, and generates the enable signals according to the decision signals and the adjusted switching sequence during a conversion phase to generate a digital output.