Latch Transient Filtering for Adaptive Single Event Upset Resistance
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Solution Overview
Problem
Existing digital circuits are vulnerable to single event upsets (SEUs) and single event transients (SETS) caused by radiation, leading to errors and performance degradation, with conventional solutions resulting in increased circuit size, slower speed, and fixed, immutable designs that do not adequately address varying radiation environments.
Innovation Solution
A digital circuit with adaptive resistance to single event upsets, featuring a novel transient filter within the feedback loop of each latch, utilizing a controllable inertial delay inverter and a standard inverter, controlled by delay locked loops to precisely manage rise and fall times, rejecting pulses of width less than the longest anticipated transient duration and allowing for flexible adaptation to different radiation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transient filtering techniques are used to reduce single event upset susceptibility, then circuit reliability improves, but circuit size increases by a factor of two to four
Solution Approach 1:
The patent applies dynamics by making the inertial delay controllable and adjustable rather than fixed. The inertial delay element responds dynamically to control signals, allowing the filtering threshold to be adapted based on radiation conditions. This dynamic control enables the same circuit to provide adequate filtering with smaller size by adjusting the delay threshold to match actual transient characteristics rather than using worst-case fixed margins.
Solution Approach 2:
The patent changes the parameter of inertial delay from a fixed value to a controllable variable. By adjusting the inertial delay parameter based on actual radiation environment and transient characteristics, the circuit achieves effective single event upset protection with reduced filtering strength, thereby reducing the required circuit size compared to conventional fixed filtering approaches.
2Reliability
If conventional transient filtering techniques are used to reduce single event upset susceptibility, then circuit reliability improves, but circuit speed decreases by a factor of two or more
Solution Approach 1:
The controllable inertial delay element dynamically adjusts its response time based on control signals. During normal operation, the inertial delay can be reduced to minimize speed penalty. When single event upsets are detected or anticipated, the inertial delay is increased to provide filtering. This dynamic adjustment resolves the contradiction by providing reliability only when needed, maintaining high circuit speed during normal operation.
Solution Approach 2:
The patent changes the inertial delay parameter from a constant slow value to a variable that can be adjusted between fast and slow states. By controlling the inertial delay parameter, the circuit achieves fast response during normal operation and slow response during upset conditions, thereby maintaining overall circuit speed while providing necessary protection.
3Reliability
If fixed filtering designs are used to accommodate worst-case variations, then circuit reliability improves, but adaptability to different radiation environments deteriorates
Solution Approach 1:
The patent applies dynamics by enabling the inertial delay to be adjusted in response to different radiation environments. Rather than being fixed for worst-case conditions, the control mechanism allows the filtering strength to be adapted to actual environmental conditions, providing both reliability and adaptability.
Solution Approach 2:
The patent changes the inertial delay parameter from a fixed worst-case value to an adjustable parameter that can be optimized for different radiation environments. This parameter control enables the circuit to maintain reliability while adapting to varying radiation conditions, resolving the contradiction between fixed reliability and environmental adaptability.
4Reliability
If stronger transient filtering is applied to reject longer pulses, then single event upset resistance improves, but legitimate signal transmission is blocked
Solution Approach 1:
The patent changes the inertial delay parameter to match the actual characteristics of radiation-induced transients rather than using excessive filtering. By controlling the inertial delay to correspond to the typical duration of single event transients, the circuit effectively rejects upsets while allowing legitimate signals with longer durations to pass through unchanged.
Solution Approach 2:
The patent applies local quality by making the filtering characteristic specific to the transient pulse duration rather than applying uniform strong filtering to all signals. The controllable inertial delay provides filtering tailored to the specific characteristics of radiation transients, rejecting only the harmful short pulses while preserving legitimate longer signals.
Data Source
AI summary
A digital circuit with adaptive resistance to single event upset. A novel transient filter is placed within the feedback loop of each latch in the digital circuit to reject pulses having a width less than T, where T is the longest anticipated duration of transients. The transient filter includes a first logic element having a controllable inertial delay and a second logic element coupled to an output of the first logic element. A first controller provides a control voltage VcR to each first logic element to control a rise time of the first logic element to be equal to T. A second controller provides a control voltage VcF to each first logic element to control a fall time of the first logic element to be equal to T.