Tristate Output Buffer Topology for Cross-Current-Free Redundancy
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Solution Overview
Problem
Existing tristate output buffers in redundant data processing systems are susceptible to radiation-related malfunctions and voltage drops due to their sensitivity and potential for cross currents, which can lead to unreliable operation, especially in space environments.
Innovation Solution
A tristate output buffer design featuring three branches, each with a buffer comprising switchable semiconductor elements of different types connected in series, with majority decision units to ensure independent control and prevent cross currents, allowing for fault tolerance and error correction by aggregating signals from multiple paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tristate output buffer is used in redundant data processing, then the ability to resolve redundancy and provide logical values is improved, but susceptibility to radiation-related malfunctions and cross currents increases
Solution Approach 1:
The output buffer is divided into three separate branches (first, second, and third branches), each with its own buffer and majority decision unit. This segmentation allows independent processing of redundant signals and isolates the impact of radiation-induced errors to single branches, enabling fault tolerance through majority voting while maintaining reliability in radiation environments.
Solution Approach 2:
Majority decision units are introduced as intermediary components between the redundant buffer branches and the final output. These intermediaries aggregate signals from multiple branches, resolve redundancy through majority voting, and prevent cross currents by ensuring only valid logical values are propagated, thereby eliminating harmful effects while preserving reliability.
2Productivity
If output buffers are used to resolve redundancy, then the processing capability is improved, but voltage drops and drive strength losses occur
Solution Approach 1:
The output buffer employs dynamic control through independently switchable semiconductor elements in each branch that can be put in conductive state independently. The majority decision units dynamically select which branch output to propagate based on signal validity, enabling the system to adapt to varying conditions and maintain optimal drive strength while processing redundancy, thereby preventing voltage drops.
3Measurement precision
If semiconductor elements are made switchable to enable tristate operation, then the logical state detection capability is improved, but cross current generation increases
Solution Approach 1:
The majority decision units provide feedback control by monitoring signals from all three buffer branches and adjusting the output based on majority voting. This feedback mechanism ensures that switchable semiconductor elements are only activated when valid logical states are detected, preventing spurious cross currents while maintaining precise logical state detection capability through coordinated control of all branches.
Data Source
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AI summary
A tristate output buffer (10) is provided which comprises a first branch (11) with a first buffer (110) and a second branch (12) with a second buffer (120). The first buffer (110) comprises: a supply port (Vdd), a ground port (Vss), an output port (Outa), two switchable semiconductor elements (Q1, Q1e) of a first type and two switchable semiconductor elements (Q2, Q2e) of a second type, wherein a switching behavior of the switchable semiconductor elements (Q1, Q1e) of the first type differs from a switching behavior of the switchable semiconductor elements (Q2, Q2e) of the second type, wherein the two switchable semiconductor elements (Q1, Q1e) of the first type are connected in series and are arranged between the supply port (Vdd) and the output port (Outa) such that they can be put in a conductive state independent of each other, and wherein the two switchable semiconductor elements (Q2, Q2e) of the second type are connected in series and are arranged between the ground port (Vss) and the output port (Outa) such that they can be put in a conductive state independent of each other.