On Thu, July 26, 2012 12:58 pm, Mark Hanchey wrote: > On 7/26/2012 12:37 PM, RussellMc wrote: >> Short : Can an MSP430 with POR, BOR and WDT be relied on to start and >> stop >> cleanly under sensible power supply on/off conditions, or are there >> known >> reliability issues. >> >> Longer: I wish to implement a microcontroller based supervisory system >> which will "ride shotgun" on a larger system and provide power good, >> startup and shut down cycling, brownout control and other housekeeping. >> The key requirement of this system is that it function flawlessly >> regardless of external events, power supply noise, power bounce and >> surges >> on startup etc. > > I would use one of the micro supervisor chips that are sold by maxim. I > like the > max6701 series, cheap and bulletproof > http://www.maxim-ic.com/datasheet/index.mvp/id/2487 > > I would then use whatever chip is needed to do the housekeeping stuff > you mentioned , and it would be a lot simpler too with the brownout and > WDT out of the way. While this sounds like a very simple thing to do- the phrase 'function flawlessly regardless of ...' leads to an outstandingly hard thing to do- hence the entire class of parts: 'Voltage Supervisors' or 'CPU Supervisors' - Microchip has a series of them: . Many choices of trip voltage, output style, output pulse width. Truly flawless is impossible, but with careful design and fault tree analysis, you can approach it- which is why these parts are are around. Adding a micro on top of it adds a much deeper level of complexity, while in theory, it could get you there, but the added complexity may make things worse when you do the fault analysis, Markov chains, etc. Regards, Matt Bennett Just outside of Austin, TX 30.51,-97.91 The views I express are my own, not that of my employer, a large multinational corporation that you are familiar with. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .