>In the end, it has to be acknowledged that you can never please all the people all the time, and have to try and strike a balance somewhere. Which is often very difficult indeed.

I suppose you know your target market better than I do, and it's presumptuous of me to think otherwise, I apologize.

>I think with my firmware changes I was able to very substantially mitigate that vulnerability but the risk is still there if extreme voltage fluctuations suddenly take place.

I think I remember reading somewhere that the control loop operates at a frequency of 1 khz?

If this is the case then the software physically cannot respond quickly enough. According to SPICE, if input voltage steps from 6 to 12 volts, with a 330u series inductor and 470u output capacitor, 1 ms is enough time for the output voltage of the 5v regulator to rise from 5v to 11v before the CPU even has an opportunity to figure out that something is wrong.

to the power supply circuit would help. At a cost of three extra parts (including a series resistor on the PWM_5V line, not pictured), a voltage excursion now immediately shuts down PWM, much faster than the CPU can react. Total BOM cost of $.10 or so?