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A. Steininger, J. Maier, R. Najvirt:
"The Metastable Behavior of a Schmitt-Trigger";
Vortrag: 22nd IEEE International Symposium on Asynchronous Circuits and Systems, Porto Alegre -- Brazil; 08.05.2016 - 11.05.2016; in: "2016 22nd IEEE International Symposium on Asynchronous Circuits and Systems (ASYNC)", IEEE Computer Society Conference Publishing Services (CPS), (2016), ISBN: 978-1-4673-9007-1; S. 57 - 64.

Schmitt-Trigger circuits are the method of choice
for converting general signal shapes into clean, well-behaved
digital ones. In this context these circuits are often used for
metastability handling, as well. However, like any other positive
feedback circuit, a Schmitt-Trigger can become metastable itself.
Therefore, its own metastable behavior must be well understood;
in particular the conditions that may cause its metastability.
In this paper we will build on existing results from Marino to
show that (a) a monotonic input signal can cause late transitions
but never leads to a non-digital voltage at the Schmitt-Trigger
output, and (b) a non-monotonic input can pin the Schmitt-
Trigger output to a constant voltage at any desired (also non-
digital) level for an arbitrary duration. In fact, the output can
even be driven to any waveform within the dynamic limits of
the system. We will base our analysis on a mathematical model
of a Schmitt-Trigger´s dynamic behavior and perform SPICE
simulations to support our theory and confirm its validity for
modern CMOS implementations. Furthermore, we will discuss
several use cases of a Schmitt-Trigger in the light of our results.

Late Transition, Schmitt-Trigger, Metastability, Asynchronous, Positive Feedback Circuit, Glitch

http://dx.doi.org/10.1109/ASYNC.2016.19