"After that, put a series resistor into your ADC from the OpAmp to limit the current to 1mA. Your ADC should be pretty happy at this point."

Maybe. Maybe not.
The ADC will almost certainly be protected against damage. However, current injection can be a problem in that it can cause error on inputs that aren't being overdriven.

To quote myself from number nine ... number nine ... number nine (sorry, White Album nostalgia)
"With many devices it is perfectly acceptable to use the internal protection diodes, but the datasheet must be reviewed carefully. The allowable current, assuming it is specified (and it usually is) can range from 2 mA to 20 mA or even 50 mA, with caveats for how many inputs can be overdriven. Again, a current limiting resistor is essential. While this may protect the inputs from damage, it may be completely unacceptable in terms of operation. I have used ADCs where all channels would be scrambled if any single channel voltage exceeded the positive supply rail by more than (as I recall) about 100 mV - far below a voltage that would be damaging. That made things very difficult."

In this case, the likelihood of current injection is so remote as to be a non-issue.

 

Thank you so much everyone. The issue is solved.

 

Thank you so much everyone. The issue is solved.

Good news!

Could you tell us what solution you chose so that other people who read this thread can benefit from your experience? What ended up working for you?

 

Good news!

Could you tell us what solution you chose so that other people who read this thread can benefit from your experience? What ended up working for you?

I connected a 300R resistor to the output and then used a clamp diode to the Vdd.

 

I connected a 300R resistor to the output and then used a clamp diode to the Vdd.

Cool, thanks for sharing, and glad it worked for you!