Programmable DAC Reference Calibration for ADC Gain Accuracy
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Solution Overview
Problem
Automotive electronic systems face challenges in accurately handling multiple analog signals from sensors due to gain inaccuracies caused by component mismatch and reference voltage variations, which affect the calibration and conversion processes in analog-to-digital converters.
Innovation Solution
A method is introduced that involves coupling a programmable reference voltage to a digital-to-analog converter (DAC) to calibrate the gain, where a predetermined input code is used to sum the DAC output with a reference voltage, and adjusting the reference voltage until the summed output is within a predetermined range, thereby minimizing conversion gain inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single analog-to-digital converter is used to handle multiple analog input signals through time division multiplexing, then device complexity is reduced, but gain inaccuracies occur due to component mismatch and reference voltage variations
Solution Approach 1:
The patent applies parameter changes by making the reference voltage programmable and adjustable. A digital-to-analog converter (DAC) is used to generate adjustable reference voltages that can be tuned to compensate for gain inaccuracies. The reference voltage parameter is changed dynamically through calibration processes, allowing the system to maintain accurate conversions despite component variations while using a single ADC.
2Device complexity
If fixed reference voltages are used in the ADC system, then circuit simplicity is maintained, but calibration accuracy is limited due to inability to compensate for component variations
Solution Approach 1:
The patent transforms the static reference voltage into a dynamic, adjustable parameter. The reference voltage is no longer fixed but can be programmed and adjusted through a DAC during calibration and operation. This dynamic approach allows the system to adapt to component variations and achieve higher calibration accuracy while maintaining relatively simple circuit architecture.
Solution Approach 2:
The patent implements preliminary calibration actions before normal operation. During the calibration phase, the programmable reference voltage is adjusted to optimal values that compensate for specific component variations in the system. This preliminary adjustment ensures that the ADC operates with high accuracy from the start, addressing manufacturing tolerances before the system enters production mode.
3Measurement precision
If programmable reference voltage with DAC is implemented for calibration, then conversion accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces a DAC as an intermediary component between the digital control logic and the analog reference voltage. This intermediary allows precise digital control of the reference voltage parameter, enabling accurate calibration without requiring complex analog adjustment circuits. The DAC serves as a bridge that translates digital calibration codes into precise analog reference voltages, improving conversion accuracy while keeping the overall system architecture manageable.
Data Source
AI summary
In accordance with an embodiment, a method of calibrating a circuit includes coupling a first reference voltage to a first input of the circuit, coupling a programmable reference voltage to a reference node of a digital-to-analog converter (DAC), such that the gain of the DAC is dependent on an input value at the reference node. The method further includes providing a first predetermined input code to the DAC, summing an output of the DAC with the first reference voltage to produce a summed output, comparing the summed output to a threshold, and adjusting the programmable reference voltage until the summed output is within a predetermined range of the threshold.