Hi Andrea,
I apologize for the delay in the response. As you have mentioned, the TLV2556 datasheet has a max peak input current rating of +/-20mA to any input, and a maximum total peak input current of +/- 30mA to all inputs combined. If the input is driven to a voltage greater than VCC+.3V; the peak input current could potentially exceed 20mA. If the +/-20mA peak current is exceeded at any time during the power up sequence, or if the device is exposed to the max rated conditions for a extended period of time during a system fault, this could affect the device reliability
Adding an external diode to divert the current to the VCC supply, in combination with a series resistor in the input path can help reduce risks of exposure to over-voltage/current conditions.
Best Regards,
Luis