Schmitt-Trigger stages are the method of choice for robust discretization of input voltages with excessive transition times or significant noise. However, they may suffer from metastability. Based on the experience that the cascading of flip-flop stages yields a dramatic improvement of their overall metastability hardness, in this paper we elaborate on the question whether the cascading of Schmitt-Trigger stages can obtain a similar gain. We perform a theoretic analysis that is backed up by an existing metastability model for a single Schmitt-Trigger stage and elaborate some claims about the behavior of a Schmitt-Trigger cascade. These claims suggest that the occurrence of metastability is indeed reduced from the first stage to the second which suggests an improvement. On the downside, however, it becomes clear that metastability can still not be completely ruled out, and in some cases the behavior of the cascade may be less beneficial for a given application, e.g. by introducing seemingly acausal transitions. We validate our findings by extensive HSPICE simulations in which we directly cover our most important claims.

中文翻译：

---

级联施密特触发器阶段会改善亚稳态行为吗？

施密特触发器级是对过渡时间过长或噪声显着的输入电压进行稳健离散化的首选方法。然而，它们可能会受到亚稳态的影响。根据触发器级的级联对其整体亚稳态硬度的显着提高的经验，本文详细阐述了施密特触发器级的级联是否可以获得类似增益的问题。我们对单个施密特触发器级的现有亚稳态模型进行了理论分析，并详细阐述了有关施密特触发器级联行为的一些主张。这些说法表明亚稳态的发生确实从第一阶段减少到第二阶段，这表明有所改善。然而，不利的一面是，很明显，仍然不能完全排除亚稳态，并且在某些情况下，级联的行为可能对给定应用不太有利，例如通过引入看似因果的转变。我们通过广泛的 HSPICE 模拟验证了我们的发现，其中我们直接涵盖了我们最重要的声明。