Suppression Effect of Ringing in Contact Discharge Waveform from Two Different ESD Generators via Ferrite Core Attached Return Current Cable

Suppression effects of a 2 m return cable with and without a ferrite core attached to its midpoint on the ringing of contact discharge calibration waveforms are investigated for two different types of ESD generators: one battery-driven and the other AC-driven generators, by comparing the measured waveforms of 4 kV contact discharge currents along with their frequency spectra. The result exhibits that the ringing of the time axis waveforms from both ESD generators can be reduced by attaching the ferrite core to the return cable at the center position compared to the normal return cable, and that the spectral variation around 100 MHz can also be suppressed due to the lower resonance Q (quality factor) values from the measured impedances of the single-ended grounded return cables. Furthermore, for the AC-driven ESD generator with a ferrite-core-attached return cable, when the charging cable is floated, the ringing is found to be significantly mitigated over the entire frequency range from 20 MHz to 200 MHz that the ringing of this kind appears, and both the time axis waveforms and spectra become closer to the IEC specified waveform and spectrum, respectively.