In an industry that once lagged in electronics adoption, today’s
automobile is at the forefront of the electronics technology curve.
The newest cars coming off the assembly line are not only pushing
the boundaries of aerodynamics and fuel efficiency, but telematics,
infotainment and cloud connectivity is revolutionizing the driving
experience. From multimedia consoles decked with high-speed data
ports to camera assisted driving systems to a plethora of GPS
antennas, the vehicles speeding along today’s highway are converging
closer to what once was only a futuristic vision.
While the marriage of the automobile and consumer electronics
improves both the safety and comfort of the driving experience, the
rise in electronic subsystems also creates new EMC compliance
challenges. Today’s high-speed automotive signal interfaces – USB,
HDMI, LVDS, Ethernet – are driven by transceiver ICs every bit as
sophisticated as the silicon enabling the newest consumer gadgets.
These high-performance transceivers are fabricated on 65 nanometer
transistor geometries and below. As silicon geometries shrink with
each revision of the IC, oxide layers become thinner and ESD becomes
more problematic. Previous generations of transceivers with a
liberal silicon I/O pad area afforded the chip designer an abundance
of chip real estate. As such, system-level circuit protection
knowledge was not as critical – the chipmaker had implemented robust
protection clamps at the I/O of the transceiver. That’s no longer
true of today’s high-speed integrated circuits.
Today’s EMC engineer, living in the sub-65nm world, knows that
relying on the on-chip ESD structures to provide a robust system
protection level is a luxury of the past. To safeguard today’s
high-speed ICs, a good EMC strategy is essential. This most
certainly incorporates a generous use of “off-chip” (external) ESD
protection components – especially in the automotive industry where
the expectations for quality and reliability are paramount. If a
consumer damages his or her cable modem router – no problem – they
can likely take the box back to the retailer and replace it with a
new router. But, what happens if they damage the USB port on their
new luxury SUV’s display console? Neither the auto manufacturer nor
the car owner is eager to support such costly replacements. As such,
the expectations for quality are higher which means the EMC
requirements are more stringent.
For ESD, at a minimum, automotive suppliers and OEMs require level 4
ESD immunity according to the IEC 61000-4-2 standard (±8kV
contact discharge, ±15kV air discharge). ESD testing is
applied to all the vulnerable data ports including keypads,
antennas, LCD displays, camera connectors, data port connectors and
bus nodes. However, many carmakers go beyond level 4 of the IEC
61000-4-2 model and impose their own specific ESD requirements. For
instance, some manufactures require ESD testing at ±25kV air
discharge and ±15kV contact discharge. They may even call out
immunity to the ISO10605:2008 ESD standard. In this case, the
passive component network is slightly modified, but the voltage
threshold is charged higher – up to ±25kV.
Join our online Radio Show on Friday 11th July starting at 2:00pm Eastern, when EETimes editor of all things fun and interesting, Max Maxfield, and embedded systems expert, Jack Ganssle, will debate as to just what is, and is not, and embedded system.