Redundant Threshold Circuits With Majority Voting for Radiation Faults
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Solution Overview
Problem
Threshold circuits in integrated circuits are susceptible to single-event effects such as transient voltage glitches caused by ionizing radiation, leading to erroneous outputs and functional disruptions in high-radiation environments, necessitating improved resilience and fault tolerance.
Innovation Solution
The implementation of modular redundant threshold circuits with a majority voter circuit, utilizing N-modular redundancy, where N≥3 threshold circuits share a common input and output connected to a majority voter, ensuring error-free digital output signals even with up to floor[(N−1)/2] threshold circuit failures, and optionally employing digital or analog majority voters to prevent ties and enhance resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If N-modular redundant threshold circuits are implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The threshold circuit is segmented into N identical modular units, each processing the same input signal independently. This segmentation allows the system to tolerate failures in individual modules while maintaining overall functionality through the majority voting mechanism.
Solution Approach 2:
A majority voter circuit is introduced as an intermediary component that receives outputs from all N threshold circuit modules and produces a single reliable output. The majority voter acts as a mediator that resolves discrepancies between modules and eliminates the need for complex error detection and correction logic in the threshold circuits themselves.
2Reliability
If redundancy techniques are used to prevent radiation-induced errors, then reliability is improved, but area increases
Solution Approach 1:
Multiple threshold circuit modules are merged into a unified redundant structure where N identical circuits share common input and output connections. The majority voter combines the outputs of these modules, allowing the system to achieve fault tolerance by combining simple, compact modules rather than implementing complex error correction within a single circuit.
Solution Approach 2:
The system changes the parameter of circuit quantity from 1 to N, where N≥3. This parameter change enables the use of majority voting logic, which provides fault tolerance with minimal area overhead compared to more complex redundancy schemes such as triple modular redundancy with additional check circuits.
3Reliability
If specialized rad-hard processes are used, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of using specialized rad-hard fabrication processes, the invention creates multiple copies (N≥3) of the same threshold circuit design using standard CMOS processes. These copied circuits are then combined through majority voting to achieve radiation hardness, eliminating the need for complex specialized manufacturing while maintaining reliability.
Solution Approach 2:
The redundant threshold circuit modules and majority voter are designed to be implemented using universal standard CMOS fabrication processes. This universal approach allows the same design to be manufactured using conventional processes available to most semiconductor manufacturers, rather than requiring specialized rad-hard processes that are available only at limited fabrication facilities.
Data Source
AI summary
Systems and methods for fault-tolerant threshold circuits used in converting an analog input to a single-bit digital output employ N-modular redundancy of either inverting or non-inverting threshold circuits whose inputs are connected to a single input, and apply majority voting of their outputs to provide correction of transient or permanent faults in up to floor[(N−1)/2] of the individual threshold circuits. Using summation to perform analog majority voting averages the N threshold circuit outputs and provides resilience to single-event transients, but may exhibit an output characteristic having intermediate voltage levels. A digital majority voter having N inputs connected to the outputs of N threshold circuits restores well-defined logic levels and clean hysteresis for Schmitt trigger threshold circuits. A single point of failure at the digital majority voter may be eliminated using an analog majority voter to sum the outputs of three or more redundant digital majority voters.