Pin Damaged question

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how can that happen??

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It can be easily achieved by applying a sufficient high overvoltage or overcurrent to the respective pin.

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and how the short is still exist even we disconnect the power from the FPGA,is it volatile??

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Simply assume, that a semiconductor structure inside the chip, e.g. an output transistor has been destroyed by applying too much energy and forms a permanent short now.

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and how to protect the I/O pins of the FPGA to not damage any more??

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Design a circuit, that keeps the FPGA's specified maximum ratings in any situation. Exposing FPGA pins directly to "outer world" should be avoided if possible, but with well designed protection networks, it can be safe.

thank you for your reply..

our application requires that the IO pins are out to the outside world..

so, can you help me suggesting some protection circuits?

thanks alot..

I read the datasheet of the IC of NXP but there is a question about the PIN number 5 VP (supply voltage), I do not understand can it be 3.3V??

I can not send the link because my post count must be 5 or greater

but it is at

nxp.com/documents/data_sheet/IP4220CZ6.pdf

I know the datasheet. You can use it with lower VCC, but the Z-diode won't limit the supply voltage above 3.3V. The clamp diodes are working anyway. You may be able to find dedicated 3.3V protection components.

You didn't yet tell about the involved interface standard and why you don't see an option to place any kind of buffer between the FPGA and the external connector.

thank you for your answers..

the I/O standard is 3.3LVTTL or 3.3LVCMOS.

and the application is writing and reading data to and from this connectors..

the IO pins are already connected to Pullup resistances outside the FPGA and the IO pins are open drain.. and the supply voltage is 3.3V.

but I do not understand something..

the function of the zener diode is to limit the voltage to 3.3V(VP), is n't it?

so any voltage above this value will be clipped to this value(3.3)..

is that true?

and the diodes are to eliminate the effect of the ESD(electrostatic discharge)..

will it work with this value(3.3V) ?

I get this IC from NXP PESDXS4UD its description is

(

Quadruple ElectroStatic Discharge (ESD) protection diode arrays in a SOT457 (SC-74)

small Surface-Mounted Device (SMD) plastic package designed to protect up to 4 signal

lines from the damage caused by ESD and other transients.

)

will it work without the zener diode?