Comparator Design: User-Defined Threshold With Asymmetrical Hysteresis

Focus:

When configuring a comparator circuit, it’s common to add hysteresis to the threshold to provide noise immunity. Typically, the designer sets a threshold with a single hysteresis value, so that in effect, there are high and low thresholds that are equidistant from the user-set threshold value. This is symmetrical hysteresis. However there are cases where we’d like to be able to configure a comparator for a threshold with asymmetrical hysteresis. For example, this approach is convenient for providing a reliable safety feature in power supplies incorporating voltage and current protection. This article presents a comparator circuit that can be used to implement asymmetrical hysteresis and derives the formulas required to set the threshold and two hysteresis values. A design example is presented and a worst-case analysis is performed to determine comparator accuracy.

What you’ll learn:

• How to implement asymmetrical hysteresis values in comparator circuits having push-pull outputs

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Author & Publication:

Gregory Mirsky, Design Engineer, Deer Park, Ill., How2Power Today, Mar 15 2021

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