input pin protection site:edaboard.com
In the automotive industry, circuits have to pass very severe votage spikes on the micro input pins.
Most micros have internal clamp diodes on the I/O pins. To limit the current into a pin configured as an input, we normally have a series resistor in the line close to the input pin, typical value of 33K. Output pins are not as susceptable to noise spikes.
Connectors to the outside world normally have 1n 200V Ceramic caps as close to the connector pin as possible to ground.
Voltage regulators are available that are automotive qualified with in-built surge and static discharge protection.
Minimum package size for resistors/Caps connected to the outside world are 0805. (Safer pad spacing).