Providing high voltage tolerance and ESD protection to MCU
What is the point of D7 anyways when you have R1/D14 right after? D7 is never going to protect anything except when the rails are unpowered but it is sized to still let your pin exceed 3.3V. And any continuous overvoltage will blow D7 anyways with no current limiting resistor before it.

I've wondered about activating before the intrinsic diodes too, but a series resistor between internal and external diode clamps should help with that. C1 should go after that resistor, not with the external clamp diodes.







simulate this circuit &ndash; Schematic created using CircuitLab

This will mess with something like a raw thermocouple input or other unconditioned sensor signals and reduce the bandwidth of all signals.

UPDATE:


  I was under the impression that esd protection diodes should be placed as close as possible to the connector, and without any resistors in the way because of the increase in inductance of longer traces and additional components. Is that not necessary? 


Trace1 doesn't have to be low in and of itself. The absolute (not relative) value of Trace2 is what matters but any excessive amount of Trace1 represents an amount that could have gone into Trace 2 instead. It is usually most practical to make Trace1 as short and low as possible than to make Trace2 very long and high so if you are working with limited space you want Trace2 >> Trace1.

Being worried about Trace1 being too high, in and of itself, is like worrying about sandbags in front of your pillbox. You want your VIP camp to be far behind your pillbox so its probably best to move the pillbox right up to the sandbags, but that doesn't mean sandbags are bad if they are there. You just don't want to make the VIP camp closer just so you have sandbags. That's a bad tradeoff.