Dual-Path Synchronizer Circuit to Block Soft Error Propagation
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Solution Overview
Problem
As device geometries shrink, synchronizer flip-flops become more susceptible to soft errors from cosmic radiation and power supply noise, leading to faults in digital systems, especially in safety-critical applications where these errors cannot be ignored.
Innovation Solution
A synchronizer circuit is designed with two parallel synchronizers and selection circuitry that compares their outputs, ensuring the output changes only if both agree, and uses stored values if they differ, thereby reducing or eliminating errors caused by soft errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometries are shrunk to improve integration density, then productivity is improved, but reliability deteriorates due to increased susceptibility to soft errors
Solution Approach 1:
The synchronizer is divided into multiple independent flip-flops (first flip-flop, second flip-flop, third flip-flop) that operate in parallel. Each flip-flop processes the input signal independently, and their outputs are combined through logic circuits. This segmentation allows the system to maintain high integration density while improving reliability through redundancy - if one flip-flop suffers a soft error, the other flip-flops can compensate.
Solution Approach 2:
Different flip-flops are assigned specific functional roles within the synchronizer structure. The first and second flip-flops capture input signals at different clock edges, while the third flip-flop performs final synchronization. This local differentiation of function allows each component to be optimized for its specific task while contributing to overall system reliability through diverse error detection paths.
2Device complexity
If a single synchronizer is used to maintain simple circuit structure, then device complexity is reduced, but reliability deteriorates due to lack of error detection capability
Solution Approach 1:
The synchronizer is segmented into multiple flip-flops with distinct functions. The first flip-flop captures the input signal on the rising edge, the second flip-flop captures it on the falling edge, and the third flip-flop performs final synchronization. This segmentation enables error detection through comparison of multiple capture paths while maintaining a relatively simple overall circuit structure using standard flip-flop components.
Solution Approach 2:
The circuit incorporates feedback mechanisms where the outputs of the first and second flip-flops are fed into logic circuits (AND, OR, NOT gates) that compare their values. This feedback loop continuously monitors for discrepancies between parallel capture paths, enabling soft error detection without significantly increasing circuit complexity. The feedback ensures that only consistent outputs from multiple flip-flops are propagated to the final output.
3Reliability
If parallel synchronizers are added to detect soft errors, then reliability is improved, but device complexity increases
Solution Approach 1:
The parallel synchronizer architecture segments the error detection function into distinct flip-flop units, each handling a specific aspect of signal capture. This modular segmentation allows the reliability improvement to be achieved through replication of proven flip-flop designs rather than creating complex new circuitry, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The circuit merges the outputs of multiple parallel flip-flops through logic circuits that combine their results. The AND, OR, and NOT gates merge the capture results from different clock edges into a single synchronized output. This merging approach allows parallel error detection paths to be consolidated into a unified output signal, improving reliability while controlling the increase in device complexity through efficient logic combination.
4Speed
If output changes are allowed to propagate immediately, then speed is improved, but reliability deteriorates due to potential soft error propagation
Solution Approach 1:
The circuit performs preliminary comparison and validation of signal values from multiple flip-flops before allowing output propagation. The logic circuits evaluate the outputs of the first, second, and third flip-flops in advance, checking for consistency before the final output is updated. This preliminary action ensures that soft errors are detected and blocked before they can propagate to downstream circuits, while maintaining fast response times through efficient logic evaluation.
Solution Approach 2:
The feedback mechanism continuously monitors the outputs of parallel flip-flops and only allows output changes when consistency is confirmed. The logic circuits provide feedback that gates the propagation of output changes, ensuring that only validated signals are transmitted. This feedback-controlled propagation maintains reliability by preventing error propagation while preserving speed through rapid feedback evaluation and conditional signal transmission.
Data Source
AI summary
A synchronization circuit includes a first synchronizer, a second synchronizer, and selection circuitry. The first synchronizer is configured to synchronize a received signal to a clock signal. The second synchronizer is disposed in parallel with the first synchronizer and configured to synchronize the received signal to the clock signal. The selection circuitry is coupled to the first synchronizer and the second synchronizer. The selection circuitry is configured to provide an output value generated by the first synchronizer at an output terminal of the synchronization circuit based on the output value generated by the first synchronizer being the same as an output value generated by the second synchronizer.