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Altera_Forum's avatar
Altera_Forum
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10 years ago

Cyclone 3 does not configure

EP3C10E144

EPCS16

MSEL=010

I designed board using circuit diagram on fig. 9-29. Performed AS programming, verified. Successful.

But device is dead. Its nSTATUS is low. Voltage: VCCIO=3.31V, VCCA=2.521V, VCCINT=1.259V.

I would say that VCCINT is out of spec (datasheet says 1.25 max for operating range). However I used EP3C25 with the same level of VCCINT voltage on another board without problems, thus I think it is not an issue.

What could be the problem?

Edit: CONF_DONE is steady low too.

Edit1: I found out that nCONFIG pin is in strange mode - 1.5V. There's 10K pull-up resistor, and initially level is high (I can see it using logic probe) but then level drops to these 1.5V and never gets back. nCONFIG wire has AS pgm connector, 10K pullup resistor and nothing else. As nCONFIG should be an input of the FPGA, the behavior of wire seems strange... Same story happens to TMS and TDI - both are pulled up to 2V5, but first becomes 1.9 and second 1.8 very shortly after powerup.

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    The E144 package has a bottom slug pad that must be grounded. It could be the slug isn't solder properly?

    Pete
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Pete, thank you. Of course it is not. How can I solder that slug if I have no access to it? Should I have made a hole in the board to access it? Where is it documented? IMHO soldering this "slug" is additional heating of the die, not a good idea...

    Edit: Well I found it in the handbook

    "The E144 package has an exposed pad at the bottom of the package. This exposed pad is a ground pad that must be connected to the ground plane on your PCB. Use this exposed pad for electrical connectivity and not for thermal purposes.". Nice. Then HOW I am expected to connect it to the ground if it is not accessible??? Why not making this pad at the top of the chip so that I can solder wire to it? In general, WTF...

    And most interesting... what I should do now - I have chip soldered. Any suggestions?
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Yes, it's a pain when hand working the boards. What we do is either solder paste it, and heat the bare board up on a hotplate with just the fpga until the paste flows, or pre tinning the board pad, then the chip pad and doing the same trick with the hotplate and a hot air gun until it flows.

    Works ok with lead solder but is a royal pain with ROHS solder. (Much more likely to thermally damage the part)

    Another option I guess would be to use an electrically conductive epoxy like http://www.mgchemicals.com/products/adhesives/electrically-conductive/silver-conductive-epoxy-8331/.

    (Although I haven't tried that)

    Note: Arctic Silver 5 won't work. It's thermally conductive but not electrically conductive even though it has "Silver" in the name.

    Pete
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Sh.t, it helped. I had small via almost at the center of the pad. I first used 0.5 mm drill to remove solder from it, then used 0.7 to increase its radius, then 2 mm and then 3 mm drill. 3 mm drill is obtuse drill - left from the cracked normal drill. So I drilled up to the pad, removing PCB internals first, then copper layer and mask, up to the white die of the chip. Then filled hole with solder at 440C, and connected with solder to the nearby capacitor's ground output. Ugly, but after first power up board started. I think next time I will do the same - make big via/metallized hole to fill at soldering time.

    Pete, thank you so much for the solution.