Max 2 IC occasionally gets destroyed

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check ALL pins between the pdf and your schematics & layout

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VCCINT and VCCIO are connected to 3.3 V; GNDINT and GNDIO are connected to 0 V; TDI, TCK, TMS and TDO are connected to pull-down resistors and to the Altera Byte Blaster; GCLK and DEV_OE and DEV_CLRn pins are used as "User I/O".

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also use Quartus -> Assignments -> Pin Planer and check all entries.

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All "User I/O" outputs pins have a high impedance load; all "User I/O" input pins have an input between 0 V and 3.3 V. All unused "User I/O" pins have either an input between 0 V and 3.3 V or are unconnected.

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check your project settings for this device how it should handle unused pins.

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They are reserved "as input tri-stated".

On the conditions above, can any cause of the device destruction be excluded except the following?

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ESD problems in your enviroment [...] voltage over and undershots on input pins, gnd bouncing

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The label on the device package says "EPM570T100C4N". This is equal to the device setting in the corresponding Quartus project.

Well, the datasheet (device handbook) does not contain the pinout, does it? Would you recommend to take the ".pin" file of my Quartus project and to compare it with the PCB schematics?

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You can use this file

http://www.altera.com/literature/dp/max2/epm570.pdf

and check ALL pins between the pdf and your schematics & layout

also use Quartus -> Assignments -> Pin Planer

and check all entries.

Next step, check your project settings for this device how it should handle unused pins.

If there is no mistake between altera documentation and your design, then check for ESD problems in your enviroment. i remember that we had a chair that was not ESD save and depending on the person some pcb were damaged due to ESD. replacing the chair with one that was ESD safe solved this problem.

Also you power suppply and or your design at all can have problems. voltage over and undershots on input pins, gnd bouncing (probably wont destroy the device)

as your problem happens on more than one pcb then it must be a design weakness, quartus settings or schematics or enviroment.

Thank you for your answer, MSchmitt.

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check the labeling on your device with the datesheet if you have the correct device mounted.

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It is the correct device. The label on the device package says "EPM570T100C4N". This is equal to the device setting in the corresponding Quartus project.

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if you use a new unprogrammed device will it be destroyed as well ?

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No, it is not destroyed, but even when it is programmed, it may work as expected. There are both cases (destroyed and not destroyed) when programmed, and there may be both cases when not programmed - but I can't verify that.

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check wheter you have two outputs connected.

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No outputs are connected with each other.

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Recheck all max 2 pins the device on the pcb as it is realy connected with the datasheet

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Well, the datasheet (device handbook) does not contain the pinout, does it? Would you recommend to take the ".pin" file of my Quartus project and to compare it with the PCB schematics?

Recheck all max 2 pins the device on the pcb as it is realy connected with the datasheet

if you use a new unprogrammed device will it be destroyed as well ?

if no check wheter you have two outputs connected.

check the labeling on your device with the datesheet if you have the correct device mounted.