Abstract
In 2008, International Electrotechnical Commission (IEC) prescribed an immunity test (IEC61000-4-2) of electronic equipment against electrostatic discharges (ESDs), and provided a theoretical ESD current based on a Heidler's formula. For the current waveform, however, not the whole waveform but only the rise time, the first peak, and the current values at 30 ns and 60 ns are specified in the time domain along with their variability so that a commercially available ESD generator (ESD gun) shall be calibrated by checking whether or not the injected current onto an IEC recommended current target meets the IEC specification. In this study, to propose in the frequency domain the allowable variability of IEC specified current waveforms, we calculated the frequency spectra of theoretical current waveforms obtained by changing the parameters in the Heidler's formula, which were compared with those of discharge currents measured for contact discharges of commercially available ESD guns onto the IEC target. Results enabled us to give the allowable variability in the current spectra with respect to the theoretical current waveform, which is from -5 dB to +4 dB up to 400 MHz and from -6 dB to +8 dB over 400 MHz, while the measured waveforms that meet the IEC standard in the time domain have the spectra greater than +8 dB over 1 GHz due to the distortion of the current rising waveforms, although they fall in the allowable range below 1 GHz.
