Kyocera AVX Electrostatic Protection Using Ceramic Capacitors
Any conductive interface between an electrical circuit and the outside world introduces the possibility of damage through electrostatic discharge (ESD). Accumulated static charge on a person, a cable, or any similar surface can readily dissipate its stored potential energy upon contact into sensitive components resulting in highly destructive currents.
Ideally, varistors and TVS diodes only activate to protect the circuit when a high voltage is present and impart no parasitic effects during normal operation. For high-speed data lines, in particular, it is critical that the protection device introduce as little capacitance as possible (Electronic Design). TVS diodes and varistors are therefore specified not only by their voltage ratings, but also by their capacitance, leakage current, and package options.
Traditional protection devices include a myriad of different varistors and transient voltage suppression (TVS) diodes. Both operate on the principle of shunting current to ground when the applied voltage exceeds a clamping threshold as shown in figure 1.
Ceramic capacitors as an alternative
In practice, many input/output (I/O) lines are not high-speed and can tolerate a fair amount
of parasitic capacitance. In these scenarios, a specialized device can be used to gain a significant
cost advantage over traditional TVS diodes and varistors: the ESD-safe multi-layer ceramic capacitor (MLCC).
These capacitors contain specialized structures that allow them to tolerate voltage impulses
orders of magnitude higher than their continuous DC rating. Examples of X7R devices are shown in
table 1. As can be seen, a common 25 V 0805 chip capacitor in this series can withstand 26 kV of ESD
The KYOCERA AVX ESD-Safe™ Series provides a wide range of ESD robust MLCC’s tested according to the
AECQ200, IEC61000-4-2, and ISO10605 standards. These capacitors offer an inexpensive alternative
to protecting I/O lines where speed is not critical. In applications where MLCC’s can not be used, it is
recommended to simply use the more traditional Multilayer Varistor (MLV).