High Speed Multimedia Interfaces and ESD

There was an article in the April 2009 issue of Conformity Magazine about input protection for high speed video type interfaces [1].  Video interface devices need to provide a lot of IO interfaces to external storage, networks, and video display devices.  Many of these interfaces are high speed and exposed to users in ESD unfriendly environments (ie carpetted living rooms).  Example interfaces are RCA I/O ports, VGA ports, IEEE 1394 Firewire ports, USB ports, eSATA ports, and HDMI ports.  The next generation of USB will be 5.0 Gbps and HDMI ports are already at 3.4 Gbps.  The article describes the characteristics of the ESD pulses that these devices must survive, but also points out another similar phenomenon of cable discharge that actually can be even more dangerous to the digital devices.  Cable discharge is refers to the discharging of any charge that is built up on a floating cable when it is plugged in to a device.  The total amount of charge is proportional to the length of the cable, and some of the interface cables can be quite long such as Ethernet that could be up to 100 m long.  The article goes on to describe the importance of considering the effect of the input protection devices on signal integrity.  It provides examples of some protection devices that are appropriate for use on high speed interfaces from Semtech.  Note that the article was written by Semtech employees so the focus was on Semtech parts only.


[1] Yang, Grace and Timothy Puls. April 2009. "Protecting Set Top Boxes from ESD and Cable Discharge Threats." Conformity Magazine. Volume 14, Issue 4.