This lesson shows how to design ESD protection for output circuits. The type of ESD event that is important to the output is the human body model. The goal is to protect the output transistors from over voltage any of it’s terminals and particularly the drain-source and collector-emitter. Also in this lesson the second breakdown of ESD clamps is discussed and how the current value of this breakdown affects the robustness of the clamp.
The R*W rule is explained and is a relationship that allows the designer to find the value of resistance to put in series with the output transistor to protect it from an ESD event. Examples are given for designing output ESD protection for various types of output circuits.
ESD output protection can have different approaches depending on the circumstances. These approaches include all the ESD current going through the ESD protection cell, some of the current going through both the protected device and the protection cell, and all of the ESD current going through the protected device which means that it is self-protecting.
Examples of the IV characteristics of four ESD output protection schemes are examined and the influence of the Miller capacitance on ESD protection is considered.
This lesson has a quiz of 10 multiple choice questions to help the student check the knowledge learned in this lesson.
Lecture Notes for Lesson 3 – ESD Output Circuit Protection