As semiconductor manufacturing geometries shrink, many system design engineers find they are spending increasing amounts of time worrying about how to select appropriate external electrostatic discharge (ESD) protection devices.

Unfortunately, there is a lot of confusion about which parameters are important when evaluating an ESD device. Issues such as working voltage, breakdown voltage, clamping voltage, dynamic resistance, and residual current are all important, but often not understood. ESD vendor datasheets can compound the problem, as they often lack critical information or even provide misleading data. One such example is the use of “low voltage” ESD protection solutions and the role that a low voltage diode plays in both signal integrity and ESD protection.

Most electronic devices designed today are required to meet a minimum of 8 kV contact discharge or 15 kV air discharge, based on the international standard IEC61000-4-2. Unfortunately, most semiconductor devices will not withstand this level of electrical stress and can be permanently damaged.

This article looks at the ESD protection situation with emphasis on low-voltage signals and designs, and explains the electrical factors and device parameters which must be considered to successfully protect a circuit and its components.