Periodic Aging Monitoring in SRAM Sense Amplifiers

Abstract

In nanometer technologies the reliability of Static Random Access Memories (SRAMs) is seriously affected by transistor Bias-Temperature Instability (BTI). In this work, a circuit for the periodic aging monitoring in SRAM sense amplifiers (due to BTI related transistor degradation) is presented. This degradation increases the input offset voltage of a sense amplifier. Periodic monitoring provides the ability to avoid SRAM failures by detecting over aged sense amplifiers (near failure) and then properly react in order to maintain the memory reliable operation. The monitoring scheme is based on a low cost differential ring oscillator, which can be easily embedded in an SRAM array without affecting the normal mode of operation.