SAR ADC Offset Correction Using DAC-Generated Comparison Voltages
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Solution Overview
Problem
Mismatches in transistors within comparison circuits of SAR ADCs cause voltage offsets, leading to errors in converting analog signals to digital signals, degrading accuracy.
Innovation Solution
An ADC with a digital-to-analog converter (DAC) that generates correction voltages to adjust comparison voltages using common mode and reference voltages, correcting voltage offsets in comparison circuits through a control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transistor mismatch in comparison circuits is present, then device complexity is reduced, but measurement precision degrades due to voltage offset errors
Solution Approach 1:
The patent applies preliminary action by performing offset correction before the main analog-to-digital conversion process. A correction voltage is generated in advance based on the common mode voltage and transistor mismatch characteristics, then applied to compensate for the offset during comparison operations, thereby improving measurement precision without requiring complete redesign of the comparison circuit
Solution Approach 2:
The patent introduces an intermediary correction voltage as a mediator between the mismatched comparison circuit and the digital output. This correction voltage, generated through a correction circuit that processes common mode voltage and reference voltages, acts as a compensating element that eliminates the harmful offset effect without directly modifying the transistor structure
2Measurement precision
If voltage offset correction is implemented, then measurement precision improves, but device complexity increases due to additional correction circuits
Solution Approach 1:
The patent merges the offset correction function with the existing digital-to-analog converter (DAC) structure. The correction circuit utilizes the same reference voltage sources and switching mechanisms already present in the SAR ADC, combining multiple functions into shared components rather than adding completely separate correction hardware, thereby limiting the increase in device complexity
Solution Approach 2:
The correction circuit is designed with multi-functionality, using the same reference voltages and control signals that serve the main conversion process. The DAC structure serves both as the primary conversion element and as the basis for generating correction voltages, making components serve multiple purposes and reducing overall system complexity
Data Source
AI summary
Provided is an analog-to-digital converter and a voltage offset correction method thereof. The analog-to-digital converter may include a digital-to-analog converter (DAC) configured to generate a first comparison voltage, a comparison circuit configured to output a first comparison result signal based on a result of comparing the first comparison voltage with a second comparison voltage, and a control circuit configured to control the DAC and output an output signal, wherein the DAC may include a correction circuit configured to generate a correction voltage by selectively switching switches connected to terminals to which a plurality of reference voltages are applied, and correct a voltage offset of the comparison circuit based on the correction voltage.