Break-Before-Make Circuit Eliminates Shoot-Through Current
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Solution Overview
Problem
Existing BB4M switching circuits are susceptible to transient and radiation-induced errors in high-radiation environments, such as outer space, due to the use of storage elements like latches and flip-flops that are prone to single event upsets (SEU).
Innovation Solution
A break-before-make (BB4M) circuit topology that eliminates shoot-through current by using digital logic gates and buffers with delay elements like resistors and capacitors, preventing simultaneous selection of channels and thus reducing radiation-induced errors, without relying on storage elements like latches or flip-flops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If storage elements such as latches or flip-flops are used in BB4M switching circuits, then the circuit can maintain state information and control channel selection, but the circuit becomes susceptible to single event upset (SEU) in high-radiation environments
Solution Approach 1:
The patent removes storage elements (latches, flip-flops) from the BB4M switching circuit, extracting the source of radiation susceptibility. The circuit achieves channel selection control without these vulnerable components, thereby eliminating SEU susceptibility while maintaining functional reliability in high-radiation environments
Solution Approach 2:
The patent replaces expensive, radiation-sensitive storage elements with simpler, radiation-hardened digital logic gates and buffers. These simpler components are more tolerant to radiation effects, providing a cost-effective and reliable solution for space applications where radiation hardness is critical
2Speed
If channels are switched simultaneously in multiplexers, then channel transition speed is improved, but shoot-through current occurs between analog inputs causing functional errors
Solution Approach 1:
The patent implements a break-before-make switching sequence where the existing selected channel is disabled before the newly selected channel is enabled. This preliminary action of breaking the current connection prevents simultaneous channel activation and eliminates shoot-through current, while the carefully designed timing maintains efficient channel transition speed
Solution Approach 2:
The patent uses periodic control signals to manage channel switching in multiplexers and demultiplexers. The control signals are timed to create a non-overlapping sequence where one channel is fully disabled before the next channel is activated, preventing shoot-through current while maintaining systematic and efficient channel transitions
3Adaptability or versatility
If multiple channels are selected simultaneously in BB4M circuits, then channel switching flexibility is improved, but cross-talk and current flow between input sources occur
Solution Approach 1:
The patent employs feedback mechanisms through digital logic gates and buffers that monitor channel selection states. This feedback ensures that only one channel is actively selected at any given time, preventing cross-talk and current flow between input sources while maintaining the flexibility to switch between multiple channels as needed
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 BB4M circuit effectively prevents shoot-through currents and cross-talk, enhancing immunity to SEU in radiation environments by ensuring only one channel is selected at a time, thereby reducing functional errors and improving reliability in high-radiation conditions.
Implementation Method 1
The pulse width of the break-before-make pulse is determined by a time constant of a resistor and a capacitor in the RC delay circuit
Implementation Method 2
Individual break pulses are generated in response to transitions in address inputs to the multiplexer by exclusive-ORing a current state of the address inputs with a previous state of the address inputs
Data Source
AI summary
A break-before-make (BB4M) circuit topology is disclosed for use with a multiplexer that eliminates shoot-through current between analog inputs and also between an analog input and analog output. The BB4M circuit generates a pulse that disables an existing selected channel before enabling a newly selected channel or gate driver, and is suitable for use in high-radiation or outer space operating environments.