i don't which voltage you use for triggering the POR chip is that important. all that is important is that you reset the microcontroller after a reasonable delay after power is applied. of course you need a voltage that matches the threshold of the device. they come in a few different thresholds to work with 3.3 5 and maybe other voltages. i use a fairly large capacitor for a long delay just to be sure. it has worked absolutely reliable. i used a dip version but i am sure you can get surface mount if space is a problem and use a tantalum cap if there is no room for an electrolytic for the timing cap. make sure the POR chip never sees sense voltage without its power supply connected. i made a shield with some of those crappy thin pin stackable headers that came with the dev shield and a bad connection to 3.3 volts killed the POR chip. not much of a loss but a waste of time figuring out why it didn't work. since then i found some better square pin stackable headers.it seems to me that this startup problem is a bug with the DUE. are there any configuration options that might fix this in the microcontroller instead of forcing us to add POR chips?
What about a 12v zener diode so it doesn't send voltage till it hits the 12 volt breakdown voltage? That's the first thing I would try if I was getting brown-outs at startup.
QuoteWhat about a 12v zener diode so it doesn't send voltage till it hits the 12 volt breakdown voltage? That's the first thing I would try if I was getting brown-outs at startup.Hi,which kind of connection do you suggest? I know the classic Zener scheme with resistor in series and Zener between Vcc and hearth. But this kind of connection only cuts Voltage when it goes above the zener limit (for what I understand).Thanks in advance,Luca