Scalable mean voter for fault-tolerant mixed-signal circuits

Redundancy techniques, such as N-tuple modular redundancy has been widely used to improve the reliability of digital circuits. Unfortunately nothing substantial has been done for the analog and mixed signal systems. In this paper, we propose a redundancy based fault-tolerant methodology to design a highly reliable analog and digital circuits and systems. The key contribution of our work is an innovative mean voter. This mean voter is a low power, small area, very high bandwidth and linearly scalable voting circuit. Unlike other conventional voters which works with odd N in an NMR, the mean voter works for both odd and even N for analog units and hence reduces the area and power further. For the proof of concept, we designed two fault tolerant analog circuits i.e. a low pass anti-aliasing analog filter and a 4-bit flash ADC. We also presented fault-tolerance mechanism in 4-bit binary adder and an FPGA cell for demonstrating its advantage in digital applications. Experimental results are reported to verify the concepts and measure the system's reliability when single upset transient may occur.