Memory Cell Self-Refresh Circuit for High-Energy Particle Upsets
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Solution Overview
Problem
Existing memory devices in aerospace applications are prone to errors due to high-energy particle collisions, which can cause transient or permanent changes in memory cell states, and current solutions like triple modular redundancy are costly and complex to implement, especially when RF functions are involved.
Innovation Solution
A memory device using a D flip-flop with an RC retention circuit and Schmitt Trigger, along with an exclusive OR function and multiplexers, automatically corrects high-energy particle collisions without the need for a refreshing clock, allowing self-refreshing of data and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If triple modular redundancy with voting element is used to correct high-energy particle collisions, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the memory cell into three separate functional copies (first, second, and third memory cells) that operate independently. Each copy processes data through its own path, allowing error detection and correction without requiring a complex centralized voting mechanism. This segmentation approach reduces overall system complexity while maintaining reliability.
Solution Approach 2:
The patent creates three redundant copies of the memory cell circuitry and data paths. By copying the essential functional elements and comparing their outputs, the system can identify and correct single-event upsets without needing complex voting logic. The copying approach simplifies the architecture compared to traditional TMR voting systems.
2Reliability
If triple modular redundancy with voting element is used to correct high-energy particle collisions, then reliability is improved, but cost increases
Solution Approach 1:
By segmenting the memory function into three independent but simplified cell copies with direct comparison logic, the patent reduces the need for expensive voting circuitry. Each segment is simpler to manufacture, and the overall cost is reduced compared to traditional TMR implementations.
Solution Approach 2:
The patent uses functional copying of memory cells with direct output comparison, eliminating the need for complex voting elements. This copying approach with simplified error handling reduces manufacturing costs while maintaining the reliability benefits of redundancy.
3Reliability
If data refresh clock is used in triple modular redundancy system, then error correction is achieved, but RF functions are disrupted due to spectral pollution
Solution Approach 1:
The patent extracts and eliminates the data refresh clock function from the system. Instead of using periodic clock signals to refresh and verify data, the system continuously monitors the three memory cell outputs and automatically detects and corrects errors without generating spectral pollution that would interfere with RF operations.
Solution Approach 2:
The memory system performs self-verification and self-correction by continuously comparing the outputs of three memory cells. This self-service mechanism eliminates the need for external refresh clocks, allowing the system to maintain reliability without generating harmful electromagnetic emissions that would disrupt RF functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a cost-effective and efficient method to correct high-energy particle collisions in memory devices, ensuring robustness against such impacts without disrupting RF functions, and is easily implementable using both ASICs and discrete components.
Implementation Method 1
said retention means comprise an electronic circuit including an electrical resistor and a capacitor
Implementation Method 2
An RC circuit for retaining the stored value in the memory cell is insensitive to high-energy particle collisions
Implementation Method 3
Using a Schmitt trigger allows the system output to transmit a ripple-free signal by eliminating internal voltage variations generated in the RC circuit due to high-energy particle collisions
Implementation Method 4
said detection means include means for performing an 'exclusive or' function
Data Source
Figure 1~2
Figure 3a~4
AI summary
The device has a retention unit (MRET) for retaining single copy of stored value (Qd) in a memory cell (CM) during specified time. A detection unit (MDET) detects a change of state of the memory cell by comparing the stored value in the memory cell with the retained value in the retention unit. A management unit (MG) determines whether a change of state of the memory cell is detected due to collision of a high energy particle. A loading of the value stored in the retention unit in the memory cell is automatically controlled when the change of state of the memory cell is detected. An independent claim is also included for a method for automatically correcting effect of collision of high-energy particles. (125).