Measurement of a timing error detection latch capable of sub-threshold operation

To take advantage of minimum energy consumption in sub-threshold, systems are required to have robustness to variability. In sub-threshold, exponential drain current dependence on the threshold voltage produces large sensitivities to variations. Adaptive systems are required to respond to these conditions. One adaptive method, called timing error detection (TED), eliminates traditional safety margins by scaling the supply voltage or frequency until timing errors. Presented here is a TED latch test circuit that makes use of sub-threshold operation. The circuit was fabricated with a 65 nm CMOS process, operates from 0.2 V to 1.2 V, and has a minimum energy point (MEP) near 0.2 V. Using a testing matrix of voltage and frequency pairs, the error rate and energy per operation were also measured.