I have a question about the secondary protection schemes for ESD for the I/O inside integrated circuits.
I understand the purpose of the two clamping diodes closest to the I/O pad.
Q1: Why is there a resistor R_ESD and then another two clamping diodes closer to the inverter? I understand that the two additional diodes are for secondary clamping closer to the inverter but what is the purpose of R_ESD?
Q2: About ESD strikes in general - I see in several places, they talk about a strike being 1000 V and also a certain amperage. Why do they sometimes specify a certain current, won't that be dictated by the resistance that the strike voltage sees?