Step Response of Discharge Current to Air Discharge and Waveform Calculation based on Admittance seen from Discharge Electrode of ESD Generator

Abstract

The step response of an ESD generator in the air discharge mode, which reflects the model-specific attributes, is stable and reproducible due to the lack of sparking. It has the potential to be a candidate for calibration requirements to enhance the reproducibility of the test results by air/contact discharge testing methods specified in IEC 61000-4-2. At present, however, it is unclear how the step response involves the current waveforms of air discharge and contact discharge. In this study, to clarify the relationship between the step response and the current waveforms of air and contact discharges, a formula of step response to the air discharge of an ESD generator is given based on the admittance seen from the discharge electrode of the generator. The step responses are calculated for three different types of commercially available ESD generators along with the corresponding frequency spectra, which are compared with the measured current waveforms of both air discharges and contact discharges, to reveal the attributes peculiar to the generators in relation to their ringing waveforms. Furthermore, the air discharge current is analyzed from the falling waveform of the spark voltage obtained from the Rompe-Weizel spark resistance law, and its calculation formula consisting of the step response and the spark current is derived. Comparison between the calculated and measured discharge current waveforms exhibits that the derived formula well represents the whole waveform of the air discharge current measured for each of the generators, and generally agrees with the first current peak waveform being determined by the spark length and the circuit properties specific to the generator.