Redundant Analog Self-Test for Persistent Circuit Discrepancies
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Solution Overview
Problem
Triple redundant circuits in radiation-hardened devices face testability issues, as manufacturing defects can remain undetected, leading to catastrophic failures during missions due to radiation strikes, as the system passes production tests even with faulty circuits operating in parallel.
Innovation Solution
A test system incorporating a majority voter circuit and a discrepancy detector with a latch, which identifies persistent disagreements between circuit outputs beyond settling time, indicating potential manufacturing defects, and uses filtering to differentiate between transient and persistent discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three redundant circuits operate in parallel with majority voting, then radiation immunity is improved, but manufacturing defects remain undetected
Solution Approach 1:
The patent applies preliminary action by performing discrepancy detection between redundant circuit outputs during production testing before the device is shipped. The test system compares outputs of multiple redundant circuits and flags devices with persistent discrepancies, thereby detecting manufacturing defects before they can cause catastrophic failures during radiation events in space missions.
2Difficulty of detecting and measuring
If production testing is performed on redundant circuits, then defective devices are identified, but transient radiation-like events may be misidentified as manufacturing defects
Solution Approach 1:
The patent applies dynamics by implementing a time-based filtering mechanism that distinguishes between transient discrepancies (radiation-like events) and persistent discrepancies (manufacturing defects). The test system monitors circuit outputs over multiple measurement cycles and only flags devices where discrepancies persist beyond a threshold duration, thereby dynamically adapting the detection criteria to differentiate between temporary and permanent faults.
3Difficulty of detecting and measuring
If all three redundant circuits must agree for pass/fail determination, then manufacturing defects are detected, but transient events cause false failures
Solution Approach 1:
The patent applies periodic action by performing multiple measurement cycles during production testing rather than a single comparison. The test system repeatedly measures the outputs of redundant circuits over time, allowing transient discrepancies to resolve themselves while persistent manufacturing defects remain detectable across all measurement cycles. This periodic sampling approach reduces false failures while maintaining defect detection sensitivity.
Data Source
AI summary
Described embodiments include a test system having first, second and third circuits having the same design and configured to receive a same input signal. A majority voter circuit has a first voter input coupled to a first circuit output, a second voter input coupled to a second circuit output, a third voter input coupled to a third circuit output, and a voter output. The output signal is equal to a signal present at least two of the voter inputs. A discrepancy detector circuit has first, second and third discrepancy inputs coupled to the first, second and third circuit outputs, respectively. A discrepancy output is configured to: provide a first logic signal responsive to the first, second and third circuit outputs having equal values; and provide a second logic signal responsive to the first, second and third circuit outputs having unequal values.