Hello Craig and Gerald.
Thank you again for the inputs. Would still really, really like to get a peek at the input protection (if any, ESD or otherwise) provided on the ADC pins as the only sure way of feeling comfortable with this. I understand that the ADC inputs are high impedance within the recommended operating region, but are you saying that these pins feed directly into an unprotected FET gate or something of that sort?
I'm using the AM335x data sheet SPRS717G revised June, 2014 and find the following in table 5-1, p. 79:
"Steady State Max. Voltage at all IO pins(8) -0.5V to IO supply voltage + 0.3 V"
also
"Transient Overshoot and Undershoot specification at IO terminal --- 25% of corresponding IO supply voltage for up to 30% of
signal period"
I think I'm hearing you say that the ADC inputs don't qualify as "IO pins" here though -- so I'm at something of a loss. The "steady state max. voltage" spec seems to imply some sort of diode clamping.
And the 1.8V issue aside, what happens if an ADC pin goes below ground for a short period? Poof?
Agree that it would be best to ban transients altogether, but I haven't found a way to do that here yet :-)