ADC Linearity Calibration Using Dual Acquisition Times
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Solution Overview
Problem
High precision analog-to-digital converters (ADCs) require costly and complex calibration processes due to the large difference in scale between most significant and least significant bits, necessitating accurate calibration to achieve desired accuracy.
Innovation Solution
The method involves generating multiple input voltages using an input voltage circuit and converting them to digital values using both longer and shorter ADC acquisition times, with logic circuitry determining calibration information and scaling ADC results to achieve accurate conversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration equipment is used for high precision ADC calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The ADC circuit performs self-calibration by comparing its own conversion results obtained through different acquisition times. The calibration logic circuitry within the ADC uses the difference between first digital values (longer acquisition time) and second digital values (shorter acquisition time) to determine calibration information, eliminating the need for external calibration equipment.
Solution Approach 2:
The calibration method changes the acquisition time parameter to obtain different sets of digital values. By performing conversions with both a first longer acquisition time and a second shorter acquisition time, the system exploits the time-dependent behavior of the ADC to extract calibration information without requiring external reference equipment.
2Manufacturing precision
If longer ADC acquisition time is used, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary calibration measurements using a longer acquisition time to establish accurate reference data. These preliminary results are then used to create calibration information that compensates for errors in faster conversions, allowing the ADC to achieve high precision without always using the longer acquisition time.
Solution Approach 2:
The calibration process uses excessive acquisition time (longer than normally required) to obtain highly accurate reference measurements. This excessive action is performed only during calibration, not during normal operation, allowing the system to achieve high precision calibration while maintaining fast conversion speeds during actual use.
Data Source
AI summary
An electronic circuit comprises an input voltage circuit, an analog-to-digital converter (ADC) circuit, and logic circuitry. The input voltage circuit is configured to generate multiple input voltages. The ADC circuit is configured to convert the multiple input voltages to first digital values using the first longer ADC acquisition time and convert the multiple input voltages to second digital values using the second shorter ADC acquisition time. The logic circuitry is configured to determine calibration information for the ADC circuit using the first digital values and the second digital values, and scale analog-to-digital (A/D) conversion results of the ADC circuit using the calibration information.