Radiation-Hardened Interleaved ADC Calibration With Three-Point Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time-interleaved analog-to-digital converters (ADCs) face challenges in calibration due to imprecise time derivative approximation, leading to error propagation and system failure, especially under radiation conditions causing single-event upsets (SEUs) and heavy ion effects, and require increasing complexity and cost to meet high sampling frequencies and resolution demands.
Innovation Solution
The implementation of a three-point calibration method for time-interleaved ADCs, which includes additional registers and computational elements to estimate a more precise time derivative, reducing error propagation and enhancing calibration efficiency, and the use of a clamped watchdog method to mitigate errors and reset values, thereby improving resilience to radiation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional two-point calibration method is used, then circuit complexity is low, but time derivative approximation is imprecise leading to error propagation and calibration divergence
Solution Approach 1:
The calibration process is segmented into multiple sampling points (first, second, and third time points) rather than using a simple two-point method. This segmentation allows for more precise time derivative approximation by capturing the signal behavior across multiple intervals, thereby improving measurement precision without excessively increasing circuit complexity.
Solution Approach 2:
The patent introduces an additional time dimension by sampling at three distinct time points (k-1, k, k+1) instead of two. This dimensional expansion enables more accurate derivative calculation through central difference approximation, resolving the contradiction between precision and complexity by adding temporal resolution rather than spatial circuit elements.
2Reliability
If calibration is performed under radiation conditions, then ADC can operate in harsh environments, but single-event upsets cause error propagation and system failure
Solution Approach 1:
The patent implements beforehand cushioning by using a watchdog mechanism that monitors calibration values and resets them when they exceed predetermined thresholds. This protective measure is prepared in advance to prevent error propagation from single-event upsets, thereby maintaining reliability in radiation conditions without requiring complex error correction codes or redundant systems.
Solution Approach 2:
The calibration system incorporates feedback through the watchdog mechanism that continuously monitors calibration register values and compares them against threshold limits. When radiation-induced errors cause values to exceed thresholds, the feedback loop triggers a reset, preventing system failure and maintaining reliable operation in harsh radiation environments.
3Productivity
If high sampling frequencies and resolution are demanded, then ADC performance meets modern applications, but circuit complexity and cost increase significantly
Solution Approach 1:
The patent implements a universal calibration approach that works across multiple sampling frequencies and resolution levels without requiring frequency-specific or resolution-specific circuit modifications. The three-point calibration method with watchdog protection provides a single, adaptable solution that maintains high productivity across GHz-range sampling frequencies while avoiding the need for complex frequency-multiplexed calibration circuits.
4Measurement precision
If calibration step size is reduced to 50 fs, then phase calibration precision improves, but calibration stability deteriorates under radiation conditions
Solution Approach 1:
The watchdog mechanism provides beforehand cushioning by establishing predetermined threshold limits for calibration values before radiation events occur. These thresholds are set to accommodate the fine 50 fs calibration steps while preventing instability from radiation-induced errors, thereby maintaining both precision and stability through pre-configured protective boundaries.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An analog-to-digital converter (ADC) includes at least first thru third ADC slices configured to sample input signal and transmit first thru third digitally converted values thereof, at least one reference ADC slice configured to sample input signal and transmit a digitally converted reference value, first thru third and reference registers coupled to first thru third and reference ADC slices, respectively, a delay register having an input and output, and configured to produce a sample time adjustment signal, where the sample time adjustment signal facilitates adjustment of a phase of a next time sampling of the input signal by the second ADC slice, and a plurality of computational circuit elements coupled to the input, output, and the registers, and configured to determine values of an error, an approximate time derivative of the input signal estimated from the third, second and first sampled time point, and the sample time adjustment signal.