A Fault-tolerant Voter Circuit in NEM Technology

Circuits implemented with micro- and nano-electromechanical (MEM/NEM) relays have the benefit of being capable of operating in environments with high temperature as well as high radiation levels. However, due to potential defects in the NEM relays, circuits using this technology exhibit poor reliability. To address this issue, design techniques that incorporate hardware redundancy are often implemented to improve reliability. A simple and well-established design technique in the domain of hardware redundancy is Triple Modular Redundancy(TMR). Systems with TMR perform a voting process on the outputs of replicated modules using a voting circuit. These voting circuits are usually unreliable because they are also susceptible to physical defects. Therefore, various voter designs have been proposed to increase the reliability of the voting circuit. However, conventional voter designs often fail when provided with inputs at undefined logic levels or significantly increase hardware overhead due to their high device count. This paper proposes a novel voter design utilizing NEM technology, leveraging the functionalities of NEM-based relays. Besides tolerating single faulty inputs, the voter can also handle single inputs at an undefined logic level. Experimental results based on digital simulations show that the proposed voter achieves a 72% reduction in device count compared to the best-performing conventional voter design investigated, while maintaining a similar level of fault tolerance.