During an ESD event, the zener diode incurs {HEAD ~ breakdown} to lower the trigger voltage of the lateral SCR device to within a range of about 5 7 Volts to thereby discharge the ESD current prior to damage of {TAIL ~ an internal circuit} being protected 
During an ESD event , the zener diode incurs { HEAD ~ breakdown } to lower the trigger voltage of the lateral SCR device to within a range of about 5 7 Volts to thereby discharge the ESD current prior to damage of { TAIL ~ an internal circuit } being protected
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH