why ggNMOS used for ESD doesn't break down under stress ?

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ajay181

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Hi all,

Can anyone explain why ggNMOS used for ESD doesn't break down under stress , eventhough gate is shorted to gnd ?
 

Since ggnmos is connected to ground, it is "off" in the normal mode of operation. But during esd event on drain side (to the net it is protecting) the parasitic BJT in the nmos (source - substrate - drain -> npn) triggers on and will discharge all the current through it. But we should make sure that BJT should not go to secondary breakdown otherwise device will be permanantly damaged.
-Dinesh
 

as Dinesh said, ggnmos as parasitic BJT does breakdwon under certain stress.
 

Everything breaks down. Although you might not see it
as long as you stay inside the box. You might like to
know, how thick the cardboard is. Given that what's
outside is not very friendly.
 

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