Virtual TMR Schemes Combining Fault Tolerance and Self Repair

Nano-electronic circuits and systems with a minimum feature size of 45 nm and below exhibit an increasing variety of defect and fault mechanisms. Their rising sensitivity to radiation and coupling induced single and multiple event upsets is one problem, new or enhanced aging processes that lead to early lifetime failures (ELF) pose another threat. The compensation of transient fault effects is a well explored area of science, while repair technologies that tackle permanent faults have so far found a broad acceptance only for embedded memories and for FPGA-based systems. In this paper we describe two alternative schemes of fault detection and on-line error correction based on virtual and time-shared triple modular redundancy (TMR). Optionally, both schemes allow for optional built- in self repair at reasonable total cost.