Engineers who work with the Controller Area Network bus might not appreciate the importance of protecting an active bus from damage caused by electrostatic discharge (ESD) "events" or over-voltage surges and transients. A CAN transceiver such as the Texas Instruments SN65HVD1050 High-Speed EMC Optimized CAN Transceiver or the Linear Technology LT1796 Overvoltage Fault Protected CAN Transceiver offer some protection, but it might not suffice.

According to Steve Corrigan of Kvaser, Inc., "Modern semiconductor components, such as low voltage MOSFETs and integrated circuits can be damaged by disturbances as little as 10 V, and their survivability is poor in unprotected environments. System engineers take on a big risk when expecting a CAN transceiver’s ESD cells to protect a bus from all transient events." Corrigan's article, "CAN Physical Layer Protection Hints," in the first-quarter 2010 CAN Newsletter, provides information designers should heed as they implement a CAN bus. Because many ESD specifications and standards usually apply to packaged electrical equipment, blindly following them can lead designers into a dead end if they try to extend them to CAN transceiver ICs.

In one hint or tip, Corrigan recommends using transient-voltage-suppressor diodes that can eliminate common-mode transients between CAN_ H and ground, CAN_L and ground, and for differential transients between CAN_H and CAN_L.

The nonprofit CAN in Automation (CiA) organization publishes the free quarterly CAN Newsletter in an online version. Engineers and designers can fill out a subscription form at: tinyurl.com/y8bdelv.

You can obtain the issue that contains Corrigan's article at: www.can-cia.org/newsletter/kbdtwnghofehj.pdf. It starts on page 34. Have you run into problems with transients or ESD events on a CAN bus? Share your ideas and solutions here.

--Jon Titus