Exploiting Parametric Power Supply and/or Temperature Variations to Improve Fault Tolerance in Digital Circuits

The implementation of complex functionality in low-power nano-CMOS technologies leads to enhance susceptibility to parametric disturbances (environmental, and operation-dependent). The purpose of this paper is to present recent improvements on a methodology to exploit power-supply voltage and temperature variations in order to produce fault-tolerant structural solutions. First, the proposed methodology is reviewed, highlighting its characteristics and limitations. The underlying principle is to introduce on-line additional tolerance, by dynamically controlling the time of the clock edge trigger driving specific memory cells. Second, it is shown that the proposed methodology is still useful in the presence of process variations. Third, discussion and preliminary results on the automatic selection (at gate level) of critical FF for which DDB insertion should take place are presented. Finally, it is shown that parametric delay tolerance insertion does not necessarily reduce delay fault detection, as multi-vdd or multi-frequency self-test can be used to recover detection capability.