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.
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,
For the life of me I can't figure it out now. I know at one time I made an undervoltage lockout circuit based on a zener, NPN, and potentimeter. Basically, with the correct breakdown voltage zener and the potentimeter, you could dial-in an undervoltage lockout. It worked really well with a voltage source like 12 volts when you wanted to output a much lower voltage like 3.3 or 5 volts. The voltage was very low till the input voltage got very close to 12 volts, then went up very fast to the 3.3 or 5 volts. It wasn't like a switch, but created a very steep angle which worked for my situation. But, maybe the Due is even more quirky.