- This paper discusses the previously unexplored initial front rise differences between Real HBM, TLP and HBM tester waveshapes. The dV/dt of the HBM test pulse amplitude below 2% has been shown to affect the high current immunity of Snapback type ESD protection circuits, and should replace the present time specification for a high voltage HBM pulse to rise from 10% to 90% of the peak amplitude, commonly known as risetime.