A monitoring circuit and method, wherein a voltage waveform having a linear falling edge is applied to a first node of at least one test memory cell (e.g., a plurality of test memory cells connected in parallel). The input voltage at the first node is captured when the output voltage at a second node of the test memory cell(s) rises above a high reference voltage during the falling edge. Then, a difference is determined between the input voltage as captured and either (1) the output voltage at the second node, as captured when the input voltage at the first node falls below the first reference voltage during the falling edge, or (2) a low reference voltage. This difference is proportional to the static noise margin (SNM) of the test memory cell(s) such that any changes in the difference noted with repeated monitoring are indicative of corresponding changes in the SNM.