Switched-Capacitor ADC Calibration Using a Supplementary DAC
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ADC testing processes require high-accuracy test equipment and lengthy calculation times to measure offset and full-scale gain error, especially for low-cost ADC devices, due to the need for non-ideal ramp signals and subsequent noise suppression, leading to increased manufacturing costs and inefficiencies.
Innovation Solution
A switched-capacitor ADC with a built-in supplementary DAC circuit that shifts the DC transfer curve to allow direct measurement of offset and full-scale gain error using on-board voltages, eliminating the need for high-precision analog sources and simplifying the test setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current ADC testing processes use non-ideal ramp signals and noise suppression methods, then measurement accuracy can be maintained, but testing time and calculation time increase significantly
Solution Approach 1:
The supplementary DAC circuit pre-shifts the DC transfer curve by a known amount before measurement, so that the measurement process directly captures the offset and gain error without requiring subsequent complex calculations or noise suppression iterations, thereby reducing testing time while maintaining accuracy
2Measurement precision
If high-accuracy test equipment is used to measure offset and full-scale gain error, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The ADC device incorporates a built-in supplementary DAC circuit that automatically performs the DC transfer curve shifting function, allowing the device to measure its own parameters using simple on-board voltages without requiring external high-precision test equipment, thus reducing both device complexity and manufacturing cost
Solution Approach 2:
The supplementary DAC circuit serves multiple functions: it shifts the DC transfer curve for offset measurement, shifts it for full-scale gain error measurement, and enables simplified INL and DNL measurements, all using the same built-in circuitry and on-board voltages, eliminating the need for specialized high-precision external equipment
3Productivity
If built-in supplementary DAC circuit is added to shift DC transfer curve, then measurement process is simplified and testing time is reduced, but device complexity increases
Solution Approach 1:
The supplementary DAC circuit is merged with the existing main DAC circuit and capacitor array of the ADC, sharing common hardware resources such as the capacitor array and control logic, so that the additional functionality is achieved with minimal increase in overall device complexity while significantly improving measurement efficiency
Data Source
AI summary
A switched-capacitor analog-to-digital converter (ADC) includes: a main digital-to-analog converter (DAC) circuit; a comparator coupled to the main DAC circuit and configured to determine whether the input to the comparator exceeds a pre-determined threshold; and a supplementary DAC circuit coupled to the main DAC circuit, wherein the switched-capacitor ADC is configured to operate in at least one of a first mode or a second mode, wherein in the first mode for measuring an offset of the switched-capacitor ADC, the supplementary DAC circuit is configured to shift a voltage at an output of the main DAC circuit by a first value having a first polarity, and wherein in the second mode for measuring a full-scale gain error of the switched-capacitor ADC, the supplementary DAC circuit is configured to shift the voltage at the output of the main DAC circuit by a second value having a second polarity opposite the first polarity.