In the ESD RC model, the HBM capacitance is 150 pF as opposed to 100 pF, and the discharge resistor is 330 ohms instead of 1500 ohms. As a result, the ESD current or energy is much more severe with the IEC model. As shown in the waveforms for 1 kV, it is noticed that the IEC61000-4-2 waveform has a higher peak transient and much more residual energy over time than the JEDEC HBM waveform. The reason this is important to understand is that IC vendors will specify ESD tolerance on their datasheets. Unless it is explicitly indicated that certain pins are specified to IEC61000-4-2 test criteria, then it is mostly referring to the JESD22-A114 HBM test standard. Do not be misled by these datasheet values if they inherently are 8 kV, for example. The reality is that without an external ESD diode protecting the IC, the pins will be damaged during IEC61000-4-2 testing, even though these pins are rated high ESD tolerance per JESD22-A114.