Post by thread:Re: [PICLIST] [EE] MTBF numbers? [ot?]

Does anyone know what the mtbf rating is for any of the pics? I've rummaged around the Microchip site but couldn't find a mtbf number. I've have a sub-board where the component cost is within pennies of using a couple of ic's or a single pic. The entire board has to be rated with a mtbf for certification purposes. I can do this with a couple of logic ic's and a transistor. I can also do this with a single pic, a diode, and a transistor. The transistor in each case is so under driven its not even on the charts aka bullet proof. The problems are simply which has highest mtbf rate and which would consume less man hours to produce. The logic ic's do the basic job , can be ordered in mil ratings and will have some flexibility. The pic on the other hand will take programing, the software needs to be certified/reviewed, but it has infinitely more flexibility in comparison. I'm curious to see which way everyone would go with this. The main criteria are reliability and production cost. And each way has its merits. Dave The only thing that helps me maintain my slender grip on reality is the friendship I share with my collection of singing potatoes \|/ ____ \|/ ~@-/ oO \-@~ /_( \__/ )_\ \__U_/ -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. The only thing that helps me maintain my slender grip on reality is the friendship I share with my collection of singing potatoes \|/ ____ \|/ ~@-/ oO \-@~ /_( \__/ )_\ \__U_/ -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 13:37 11/05/2001 -0800, Dave King wrote: >Does anyone know what the mtbf rating is for any of the pics? >I've rummaged around the Microchip site but couldn't find a >mtbf number. > >[...] >I'm curious to see which way everyone would go with this. The main >criteria are reliability and production cost. And each way has its merits. Interesting question -- unluckily I don't have a clue about mtbf numbers for PICs. My guess would be though that the discrete logic is way more reliable. It also seems that production cost is not higher -- leaving the lower flexibility as sole disadvantage. If your main criteria are reliability and production cost, I'd probably go with discrete logic. ge -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Oh, you all can't be serious! It took me all of 60 seconds to find this on Microchip's site: http://www.microchip.com/1010/overview/qualreli/relidata/index.htm Would nothing there be helpful? Dale -- Hallo, this is Linus Torvalds and I pronounce Linux as Leennuks. Hallo, this is Bill Gates and I pronounce 'crap' as 'Windows'. On Mon, 5 Nov 2001, Gerhard Fiedler wrote: {Quote hidden}> At 13:37 11/05/2001 -0800, Dave King wrote: > >Does anyone know what the mtbf rating is for any of the pics? > >I've rummaged around the Microchip site but couldn't find a > >mtbf number. > > > >[...] > >I'm curious to see which way everyone would go with this. The main > >criteria are reliability and production cost. And each way has its merits. > > Interesting question -- unluckily I don't have a clue about mtbf numbers > for PICs. My guess would be though that the discrete logic is way more > reliable. It also seems that production cost is not higher -- leaving the > lower flexibility as sole disadvantage. If your main criteria are > reliability and production cost, I'd probably go with discrete logic. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 10:43 PM 11/5/01 -0600, you wrote: >Oh, you all can't be serious! It took me all of 60 seconds to find this >on Microchip's site: > >http://www.microchip.com/1010/overview/qualreli/relidata/index.htm > >Would nothing there be helpful? Now read through all of that and pull out just one mtbf number... -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

At 07:08 AM 11/6/01 -0800, Bob Ammerman wrote: >I am not an expert on these things, but I believe that all the numbers that >mChip thrwos about in this data are the raw materials from which one can >compute an MTBF, if one knows the appropriate incantation. Anyone notice that the only acceptable MTBF calculation is: MTBFours >= MTBFcompetitor_published If the number that you get after a bunch of research dosen't meet this, then they tell you it's "unacceptable", even if you calculate the other guy's and it differs significantly from what they publish. -- Dave's Engineering Page: http://www.dvanhorn.org Got a need to read Bar codes? http://www.barcodechip.com Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with two or five digit supplemental codes, in an 8 pin chip, with NO external parts. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

> I am not an expert on these things, but I believe that all the numbers > that mChip thrwos about in this data are the raw materials from which > one can compute an MTBF, if one knows the appropriate incantation. MTBF computation requires some sort of failure mode prediction or analysis. If you accept a hardware that is perfectly working then you can predict a software glitch by using the S/N in the circuit and the respective logic levels and their margins. Then you can come up with a number of seconds required for a 50% probability that a logic state will be misread and cause a glitch, for each pin. The total will refer to all the pins. So having a very low number of IOs and redundant IOs helps. As Alan Pearce said, it is related to the number of joints... With a computer, that can try to re-read inputs and use redundant outputs this computation becomes very complex. However normal logic circuits stop here and computers can be more reliable that normal logic because of it (computers can try harder). Chip internal logic is considered very reliable (unless it is made or designed by certain manufacturers <g>). I think that no manufacturer who has the disclaimer about his products not being usable for 'life support' and 'critical' applications will ever give a MTBF figure without the lawyers smothering it instantly. Peter -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu