A Fault Tolerant Voter for Approximate Triple Modular Redundancy

Abstract

Approximate Triple Modular Redundancy has been proposed in the literature to overcome the area overhead issue of Triple Modular Redundancy (TMR). The outcome of TMR/Approximate TMR modules serves as the voter input to produce the final output of a system. Because the working principle of Approximate TMR conditionally allows one of the approximate modules to differ from the original circuit, it is critical for Approximate TMR that a voter not only be tolerant toward its internal faults but also toward faults that occur at the voter inputs. Herein, we present a novel compact voter for Approximate TMR using pass transistors and quadded transistor level redundancy to achieve a higher fault masking. The design also targets a better Quality of Circuit (QoC), a new metric which we have proposed for highlighting the ability of a circuit to fully mask all possible internal faults for an input vector. Comparing the fault masking features with those of existing works, the proposed voter delivered upto 45.1%, 62.5%, 26.6% improvement in Fault Masking Ratio (FMR), QoC, and reliability, respectively. With respect to the electrical characteristics, our proposed voter can achieve an improvement of up to 50% and 56% in terms of the transistor count and power delay product, respectively.

New hardware redundancy approach for making modules tolerate faults using a new fault detecting voter unit structure

“…The voter unit produces the output of the main system based on the majority votes. ATMR can be developed using approximate modules for all three modules of TMR system [14]. The output of the approximate modules differs from the original circuit for some of the input vectors, which helps in complexity reduction.…”

“…In [14], a novel fault tolerant voter unit with superior electrical features designed using pass transistors and qaudded transistor redundancy is presented. The use of pass transistors aided in designing the voter unit with reduced number of transistors which causes minimum voter internal faults.…”

“…MMR needs at least two healthy modules to be connected to the majority gate and one healthy module for the minority gate in order to produce the correct result. In [14], the design of an approximate TMR (ATMR) with a fault tolerant voter is presented. ATMR has been proposed in the literature to overcome the area overhead issue of TMR.…”

Using Approximate Computing and Selective Hardening for the Reduction of Overheads in the Design of Radiation-Induced Fault-Tolerant Systems

“…These works have shown good results by compensating the costs of fault tolerance techniques with the speed-up obtained through AC. However, most of the works presented are at the circuit level [10,[31][32][33][34] or require special architecture [9,29,35,36], so hardware modifications are still necessary. This means that those works are not suitable for COTS processors.…”

Fault Tolerant Digital Data-Path Design via Control Feedback Loops

“…Reduced precision replicas can also be used in a dual manner, with the lower cost data-path working in a higher supply voltage domain and providing a highly reliable reference [8]. Other works improved reliability by increasing the resilience of the voting circuits within the TMR, such as the self checking voting circuits [9], adaptable bit-width voter [10], or employing dedicated voters for approximate TMR [11].…”