ProTek Devices’ Ian Doyle contributed an article to EE Journal that was published Nov. 4, 2014. An excerpt follows and the full article can be read at EE Journal…
Overvoltage Protection in High Speed Communication Ports
by Ian Doyle, ProTek Devices
Editor’s Note: While Amelia’s Halloween Fish Fry had us all running out and gleefully building our own singing Tesla coils, and even though shuffling quietly across the carpet and sending a bright 10,000-volt arc from your fingertip to a napping family member can be a barrel of laughs, there are times where we most definitely do not find electrostatic discharge so amusing. The first of those, of course, is when we ARE the sleeping family member. Sheesh, what an insensitive prank!
But, a second scenario where we do not welcome the effect of high-voltage static discharge events is when we’re designing high-speed communications circuits. Getting your Ethernet port zapped with a 10kV ESD is far from fun – especially for the Ethernet port. But, how do we help our circuits protect themselves? Ian Doyle of ProTek devices has some very helpful suggestions.
–Kevin Morris, Editor-in-Chief
Transmission data rates continue to grow and grow to meet consumer demands for multimedia rich content, such as streaming video. In turn, whether in the home or at the backend, Ethernet connectivity also continues its widespread use. As a result, and more than ever, electrostatic discharge (ESD) transient threats pose challenges to system designers to incorporate overvoltage protection that doesn’t impact performance.
The International Electro-technical Commission (IEC) has defined a Human Body Model (HBM) ESD event. The intent is to guide designers in implementing adequate protection in their electrostatic applications. The IEC defined the HBM ESD discharge impulse, with four levels in standard 61000-4-2. It has a rise time of less than 1 ns and decay time of 60 ns.
As a system requirement, the four levels of IEC 61000-4-2 cover up to ±8 kV contact / ±15 kV air discharges for ESD transients in systems. In some applications a higher level is specified for enhanced contact and air discharge specifications. This is because human body models can reach ±25 kV in static-rich environments. Read more.