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ESD protection circuit diode

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neoflash

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attached is a figure of normal esd circuit.

we have three diodes:

Zenner diode and diode to PWR will protect circuit when power pin is floating.

However, what about when esd happens, the ground pin is also floating, what is the discharge path? to substrate?
 

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IanP

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This is hypothetical situation ..
If the "ground pin" is floating you wouldn't call it ground ..
In this case it is an isolated "system" and there is no discharge path to enywhere ..
"System" will be charged and will remain in this condition till a discharge path is created, somehow ..

Regards,
IanP
 

    neoflash

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neoflash

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exactly! I got stuck there, thanks.
 

Teddy

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ESD is tested as pinX to pinY while all others are floating. That said there is the same structure on "the other side" which allows you to have "conductive" path and dissipate ESD pulse.
Also you have to remember that in case of ESD you are usually breaking through the junctions otherwise the ESD protection would mess up the circuit.
 

    neoflash

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pillar_chen

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There are other discharge path through gnd
 

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