Multilayer Varistors in Automobile MUX Bus Applications

The purpose of this paper is to discuss methods available to designers to suppress ESD and control EMI on automobile multiplexed data lines. Multiplex standards (such as J1850) have created complex networks of sensors and controls within automobiles which are prone to damage by ESD. Further, as communication speeds increase, the networks EMI/RFI performance becomes of greater importance. Both issues must be addressed by designers in order to guarantee long term reliability of the network.

There are many methods in which designers have dealt with EMI and ESD transient voltage problems. Some designers used R/C networks, L/C networks or back to back Zeners with an EMI capacitor. Others relied upon internal protection of the IC to handle suppression. A relatively new method utilizing Multilayer Varistors (MLVs) was found to have both electrical and size advantage over most if not all previous suppression/control methods.