System-ESD validation of a microcontroller with external RC-filter

Although microcontrollers are generally well separated from ESD events happening on a fully equipped and mounted electronic control unit, special configurations expose some microcontrollers to these system-ESD events. In the BISS IC EMC Test Specification [1], several system-level disturbance tests are referenced. One of them is the unpowered system-ESD test according to the international standard ISO 10506 [2]. Automotive companies request that microcontrollers and other ICs shall withstand e.g. 6 kV system-ESD stress applied to IC-pins either directly or via discrete protection components. This paper describes the experience made with a 65 nm CMOS 32-bit microcontroller including an external ESD protection filter when exposed to normative system-ESD pulses. Although not expected, discrete SMD protection capacitors degraded or even showed short-circuits after being exposed to several ESD events.