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Article #1046Re: Need for more expertise on IC's
From: Dave Langstaff
Date: Wed, 24 Apr 2002 11:52
Date: Wed, 24 Apr 2002 11:52
35 lines
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2786 bytes
"Jim Lazzaro" <jim_lazzaro@hotmail.com> wrote in message news:f666726f.0204220754.6e06e372@posting.google.com... > The question is: when an IC is found to be running very hot, what > things could be the coulprits other than itself? > So far I can think of higher supply voltage or some faulty capacitor > or a heavier load(ex. a shorted component) on its output. > Thanks > JIM You don't say what sort of logic family the chip is. If it is cMOS, then, if one of the outputs hasn't been properly protected internally and you try driving an inductive load with it, it is possible to push the output voltage on the pad beyond the power supply rails. At that point the thyristor that lurks hidden within the complementary output transistors will trigger, causing a virtual short circuit across the power rails. This usually causes a lot of heat, this is known as latch-up and quite often results in molten silicon and the escape of magic smoke. Another possibility is that more that one output has been enabled to talk to a tri-state structure. Both chips involved will tend to get warm, although not usually as hot as latch-up. The power consumption of cMOS circuits is dependent on clock frequency, so if you are clocking stuff much faster that its designed for, you will get heat. Hope these help you try and narrow down the options. regards dave L
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 105d97,35d11a5b6c339d46 X-Google-Attributes: gid105d97,public X-Google-Thread: 1131b0,35d11a5b6c339d46 X-Google-Attributes: gid1131b0,public X-Google-Thread: 103407,35d11a5b6c339d46 X-Google-Attributes: gid103407,public X-Google-ArrivalTime: 2002-04-24 04:52:08 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!kibo.news.demon.net!demon!xara.net!gxn.net!server5.netnews.ja.net!news.swman.net.uk!not-for-mail From: "Dave Langstaff" <dpl@aber.ac.uk> Newsgroups: sci.electronics.repair,aus.electronics,sci.electronics Subject: Re: Need for more expertise on IC's Date: Wed, 24 Apr 2002 12:52:19 +0100 Organization: Prifysgol Cymru - University of Wales, Aberystwyth Lines: 38 Message-ID: <1019649142.783608@dyfi> References: <f666726f.0204220754.6e06e372@posting.google.com> NNTP-Posting-Host: dyfi.aber.ac.uk X-Trace: mannews.swan.ac.uk 1019649124 9676 144.124.16.27 (24 Apr 2002 11:52:04 GMT) X-Complaints-To: usenet@news.swman.net.uk NNTP-Posting-Date: 24 Apr 2002 11:52:04 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Cache-Post-Path: dyfi!unknown@pcedfj.dph.aber.ac.uk X-Cache: nntpcache 2.4.0b5 (see http://www.nntpcache.org/)