Comparator Metastability in the Presence of Noise

Metastability is the inability of a latched comparator to reach a decision in the available amount of time. Existing analyses of metastability disregard noise, treating it as a deterministic phenomenon that inevitably happens every-time the input voltage, upsilon(Idiff), falls in a certain interval around 0, and which is restricted to the aforementioned interval. Also, according to the conventional analysis, the decision takes an infinite amount of time if upsilon(Idiff) = 0 This work analyzes metastability in the presence of noise, showing it is actually a random phenomenon whose probability of occurrence is derived. It is concluded that there is no input value for which metastability inevitably occurs (not even upsilon(Idiff) = 0), and that there may be a significant probability of metastability at input voltage values much larger than those predicted by conventional analysis. All the theoretical results are in agreement with extensive HSPICE transient noise simulations.