ESD Generator Tip Current Reconstruction Using a Current Probe Measurement at the Ground Strap

Abstract

Monitoring ESD generator discharge current during IEC 61000-4-2 testing helps to better understand product failures. By acquiring the discharge waveform using an oscilloscope, this enables the operator to both document the current waveform which resulted in product failure, and to identify the presence of secondary ESD event within the product. Placing a current probe such as an F-65 current clamp at the tip of the ESD generator may change the discharge current waveform shape due to probe loading. In addition, the inclusion of an extra cable and current clamp increases physical weight at the tip of the ESD generator and reduces operator convenience during testing. In order to overcome the probe loading effect, a non-intrusive measurement method of positioning the F-65 current clamp at the ground strap of the ESD generator is proposed. The disadvantage of this configuration is that the captured waveform does not include the initial high-frequency peak current directly. Since the waveform measured at the ground strap does not contain high frequency components, mathematical processing is needed to reconstruct the initial nanosecond high-frequency current waveform which may lead to product failure. The goal of this work is to reconstruct the high-frequency discharge tip current waveform by measuring the current on the ground strap and applying deconvolution. The deconvolution method is first validated using circuit simulation. In addition, measurements are performed with different ESD generators to determine the effectiveness of the reconstruction algorithm.