TMR Sequential State Elements With Spatial Separation for Soft Errors
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Solution Overview
Problem
Existing triple-mode redundant (TMR) state machines are inadequate in high radiation environments due to 'domain crossing' errors caused by charge collection, which affects multiple circuit copies and thwarts self-correction mechanisms, particularly in Field Programmable Gate Arrays (FPGAs) and Application Specific Integrated Circuits (ASICs).
Innovation Solution
The design of triple-redundant sequential state (TRSS) machines with synchronized clock signals and self-correcting mechanisms, including a sampling stage and feedback stage, to ensure adequate spatial separation of critical nodes and implement majority voting for error correction, ensuring robustness against radiation-induced soft errors. Additionally, the physical placement of redundant pipeline blocks is strategically arranged to maintain critical node spacing, preventing charge collection from affecting multiple circuit nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard CAD software is used to minimize delay and power by placing logic nodes as close to each other as possible, then productivity and energy efficiency are improved, but reliability deteriorates due to insufficient spatial separation of critical nodes making the circuit vulnerable to radiation-induced soft errors
Solution Approach 1:
The patent applies local quality by implementing different spatial separation requirements for different circuit regions. Critical nodes that require radiation hardness are placed with adequate spacing to prevent charge collection from affecting multiple copies, while non-critical nodes can be placed closer together to maintain productivity. This localized approach to spatial separation allows the design to optimize both reliability for critical functions and productivity for overall circuit density.
2Area of stationary object
If redundant circuit copies are placed close together to minimize area, then area usage is improved, but reliability deteriorates because charge collection can affect multiple circuit nodes simultaneously, defeating the self-correcting mechanism
Solution Approach 1:
The patent applies segmentation by dividing the circuit into distinct spatial zones with different placement constraints. Redundant copies of critical state elements are segmented and placed in separated regions with adequate spacing between them, while non-critical logic can be placed more densely. This segmentation ensures that charge collection from a single radiation event cannot simultaneously affect multiple redundant copies, preserving the self-correcting capability while managing overall circuit area.
3Reliability
If adequate spatial separation of critical nodes is enforced to prevent charge collection from affecting multiple copies, then reliability is improved, but device complexity increases due to constrained placement requirements
Solution Approach 1:
The patent applies parameter changes by modifying the placement parameters and constraints in the CAD tool to automatically enforce adequate spatial separation of critical nodes. Rather than manually managing complex placement requirements, the invention changes the placement parameters (such as minimum spacing constraints for critical nodes) to incorporate radiation hardness requirements directly into the automated placement process, thereby improving reliability while managing device complexity through parameter-based control.
Data Source
AI summary
The disclosure relates generally to triple-redundant sequential state (TRSS) machines formed as integrated circuits on a semiconductor substrate, such as CMOS, and computerized methods and systems of designing the triple-redundant sequential state machines. Of particular focus in this disclosure are sequential state elements (SSEs) used to sample and hold bit states. The sampling and holding of bits states are synchronized by a clock signal thereby allowing for pipelining in the TRSS machines. In particular, the clock signal may oscillate between a first clock state and a second clock state to synchronize the operation of the SSE according to the timing provided by the clock states. The SSEs has a self-correcting mechanism to protect against radiation induced soft errors. The SSE may be provided in a pipeline circuit of a TRSS machine to receive and store a bit state of bit signal generated by combinational circuits within the pipeline circuit.