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ESD for VDD and VSS pins

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shanmei

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esd for vdd and vss pins

For the normal input and output pins, the pdiode and ndiode are used for the ESD protection.

Then how about the VDD and VSS pins? Which kind of ESD are required to protect vdd and vss pins? Thanks.
 

Re: esd for vdd and vss pins

Hi,

Internal diodes are usually too small for true ESD currents. True ESD protection usually need external protection circuitry.

VCC pins should have ceramics decoupling capacitors close to the pins and additionally a larger bulk capacitor.
The capacitors should be able to store the ESD energy without causing too high voltage.
VSS usually is GND and thus the voltage reference. It is by definition 0V.

An ESD is no circuit, but it is a high voltage, high current pulse. But due to it's short time it is relatively low energy.

Klaus
 
Re: esd for vdd and vss pins

A well done ESD pad library would include the core clamps
that complete the current loop. Could be GGNMOS, could
be active triggered, could be the two combined. A back
diode from vss to vdd should be part of the core clamp.
You may find these as part of corner bussing cells, too,
depending on who did the architecting and what kind of
library (std cell with common pads, this is likelier; analog
with bare pads only, not so much).

You could look at the ESD or I/O libraries documentation
and find out whether such a thing is provided. If not,
welcome to the fun.
 
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