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Altera_Forum
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Honored ContributorCPLD EPM240T Serious Burn down!!
Hi,I met a very bad problem when I use CPLD EPM240T.
(1) Environment : in this project,it have 10 IO board with EPM240T,all these board connected through one back board.Between these EPM240T,there is one sigle connection without any RESISTOR,this sigle connection is used EPM240T PIN-77,and all EPM240T PIN-77 are set as input. (2)Problem:when insert these IO board into back board,EPM240T will burn down after power-on delay,not all EPM240T will burn down,but at least two nearby,sometimes 3 or 4,the rest board are work well.After burn down,there is short circuit in EPM240T between VCC and GND.It's confuse that this problem is not happen everytime,and cannot reappear. (3)Question:There are at least two board burn down nearby shows that should be something cause this problem with connection between these EPM240T.All connected pin are set as input,is this a reason cause the burn down problem??Why this problem happen?Is there any one meet this problem?Could anyone help me?14 Replies
Altera_ForumThe system is grounded properly,and power supply seems Ok,no avoltage surge.
Today I found that there three pins connect to CPU pin which define as output,but not assign these pin as input or output in Quartus II.And I cut the connection between CPLD and CPU,and measure voltage: 3.3V at CPLD pin,2.0V at CPU pin.Someone says that the pin without assignment will be stuck to GND by Qaurtus II automatically.How Quartus deal with the pin without assignment??stuck to GND or stuck to VCC??Is this the reason cause CPLD damage for over current flowing from CPU to CPLD?- Altera_Forum
Are the system and operator properly grounded when the boards are inserted? There could be an ESD when the connectors touch. You can avoid it by having everything grounded before insertion, or ensuring that the boards ground touch before any other contact.
Other than that I think too that there could be a problem with the voltage supply. - Altera_Forum
This problem is not usually come out,and I don't know how to reappear it,it work well almost time.
- Altera_Forum
Even a short circuit of one or more output pins, although violating the maximum ratings, isn't usually causing catastrophic failure of the device. Thus I assume, that a serious problem of violated supply or input voltage ratings is present in your design.
