Transients, ESD and EMI in an untethered world -

Transients, ESD and EMI in an untethered world


One of my favorite Jack Ganssle’s Break Point blogs, “ESD and EMI: The Ghost in our Machines,” deals with the ongoing challenge of unpredictable transients due to electromagnetic interference (EMI), electrostatic discharge (ESD), and electrical overstress (EOS) in every embedded design. I reread it once in a while for reaffirmation and consolation.

While such ghosts have always been with us, I’ve been rereading the article more often these days because of the new markets in which increasingly untethered and self-powered wireless embedded designs must operate. Such markets present new challenges to keeping those ghosts under control. There are several reasons for this, as a survey of any consumer electronics venue, such as the upcoming 2014 CES, illustrates.

First, the consumer mobile and embedded consumer device industry is demanding the highest speed and the highest functional density out of the devices they use, but at ever lower power consumption. To do achieve that they are pushing semiconductor manufacturers and processor vendors toward circuits fabricated at sizes as small as 20 to 50 nanometers. At such geometries, the operating voltages of such ICs and devices are scarcely different than those of ESD transients that plague embedded systems. Accidents waiting to happen?

Second, these untethered powerhouses are increasingly dependent on batteries, such as the ubiquitous zinc- or lithium-powered button cells. But as Jack Ganssle has pointed out in such articles as “A sneak preview,” and “Assumptions,” the specifications for such button cells as the CR-2032 are a bit blurry and testing is a challenge, another accident that may be waiting to happen.

Third, mobile and untethered embedded device makers are now looking at such technologies as supercapacitors in combination with batteries as a way to store harvested energy for later use. While much of the work with SuperCaps has been focused on their use as an alternate method of storing energy in electric autos, a few companies, such as Cellergy, have developed techniques for their use in mobile devices and wireless sensors networks (aka the Internet of Things ).

Fourth, there is the problem of the transient-rich environment in which most mobiles and wearable consumer devices operate: the human body, which not only generates its own EM signals but is a natural self-regenerating source of electrostatic discharge.

Currently, the voltage spike sensitive capacitive touch interfaces on most mobile phones are only one (finger) touch away from disaster due to ESD and EMI transients. Now with wearable electronics there is not only that problem, but conditions that might make it worse: the moisture that the human body produces and the rain of “dust” due to skin and hair shedding.

Considerable work has been done on resolving such ESD, EMI, and transient ghost problems in a wide range of embedded applications, and much of it is and can be adapted to use in this new and dangerous device environment. Some of the work of embedded developers will have to do to address the new challenges is a matter of doing our homework, sorting out what is known and can be useful from what is not, and what else needs to be done.

To help you in that direction, this week’s issue of the Tech Focus Newsletter on “ESD/EMI challenges of nextgen connected and mobile designs , ” contains a range of design articles and other resources to help, including my Top Picks:

Improving the transient immunity of MCU-based embedded design
A five part series from Ross Carlton at Freescale Semiconductor that takes you through step by step through the EMI and ESD problems that may be faced in embedded designs and provides a range of possible solutions.

EMI Problems? Just the facts please.
In this five part series, TI’s Bonnie Baker provides a hands on tutorial on electromagnetic interference in a variety of embedded designs, how to identify the sources, the extent of the damage and what to do to both prevent and correct the problems.

I n addition, there are a number of in-depth, back-to-the-basics tutorials that I have found useful in sorting through the technical issues, including:

Testing system design components for electromagnetic interference problems
A guide to designing for ESD and EMC
The Changing ESD Landscape, and
System-Level ESD/EMI Protection Guide

However, this challenging transient ESD and EMI environment will require that we continue to come up with adaptations and extensions of what we know. New tools and alternatives are needed. I will be working to find such resources for you. But I also I look forward to your contributions to on this topic: problems you are facing and how you solved them, and resources you have found that are useful in your designs. Site Editor Bernard Cole is also editor of the twice-a-week newsletters as well as a partner in the TechRite Associates editorial services consultancy. He welcomes your feedback. Send an email to, or call 928-525-9087.

See more articles and columns like this one on up for the newsletters . Copyright © 2013 UBM–All rights reserved.

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