Article View: sci.electronics
Article #9460The 555
From: Richard S D'Ippolito
Date: Fri, 11 Jan 1991 18:55
Date: Fri, 11 Jan 1991 18:55
19 lines
1406 bytes
1406 bytes
If my memory is serving me correctly, I seem to recall (from 10 or more years back!) that there is a fundamental design flaw with the 555 timer chip, in that there are certain operating conditions and external part values which could cause part of the chip circuitry to latch up (like a thyristor), a condition requiring power removal to reset, making the 555 definitely unsuitable for a watchdog design. My further recollection is that the flaw was publically aired in some of the professional/trade magazines, such as EDN, causing no little excitement for the original manufacturer. Can anyone verify or refute this and point me to the information? Am I thinking of another chip? If true about the 555, does anyone know if this design was corrected or know of a prefered replacement part? Thanks, Rich
Technical Details
Message-ID:
<10014@as0c.sei.cmu.edu>Path:
arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!apple!julius.cs.uiuc.edu!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!fs7.ece.cmu.edu!sei!rsdShow Full Headers
Complete Article Headers
Path: arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!apple!julius.cs.uiuc.edu!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!fs7.ece.cmu.edu!sei!rsd From: rsd@sei.cmu.edu (Richard S D'Ippolito) Newsgroups: sci.electronics Subject: The 555 Message-ID: <10014@as0c.sei.cmu.edu> Date: 11 Jan 91 18:55:50 GMT Organization: Carnegie-Mellon University (Software Engineering Institute), Pgh, PA Lines: 19