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Altera_Forum's avatar
Altera_Forum
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15 years ago

CPLD 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?

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  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    So,the power system is very important,in this such of structure,hot-swap chip in every hot-swap board is necessary!

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hot-swap circuitry is only necessary when you actually do hot-swapping. From what I understood from the first post, the system is powered on after the boards have been inserted, so a hot-swap circuit won't help.

    As FvM said (and it was his assumption that was right, not mine ;) ) the only viable way is to fix the power supply. Any other correction such as a soft start on each board is just like a patch made with strings and duct tape. It may work on the short term but it's just asking for trouble on the long run.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    How can I deal with the surge when insert the IO board to back plane if a hot swap controller can't fix it?

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    I'm taking as granted, that you don't intend hot swap, insertion of boards with powered backplane. Under this assumption, I completely agree with Daixiwen "the only viable way is to fix the power supply". The power supply must have efficient means to strictly avoid overvoltages that are at risk to damage the connected equipment. We don't know however the energy involved with the surge. If it's low, TVS diodes at the boards may help. A "V"LDO ("very" low drop out voltage regulator, some have drop out voltages of 50 to 100 mV) can be an option, otherwise a special designed supply disconnector with a FET switch.