Sorry, Abhishek, updated datasheet has renumbered figures.

Have a look at figure 8 of:

http://www.analog.com/UploadedF...D630_d.pdf

Like Rob already stated, you could use a Schottky diode, reducing voltage drop to about 300mV. I have also seen sometimes AA119, which is a low ohmic germanium diode. But, be aware, that at temperatures above about 80°C this diode mutates to a low ohmic resistance, loosing all it's pn-junction characteristics.

Negative voltages at input, or voltages beyond Vcc should always be avoided. It's not static voltage of voltage drop across conducting diode, alone, what counts. Comparing -0.3V of Schottky diode with maximum negative input voltage of -0.5V, there seems indeed to be enough headroom. But don't forget ground bounce of mcu, caused by non-avoidable inductivtiy of 0V connection from die to 0V terminal of package. Ground bounce cannot be avoided by power supply decoupling, because capacitors should sit directly at die, and not at package, what's of course impossible. Ground bounce is also in the range of some 100mV, but with highly capacitive loads it can be much higher!! So, the headroom of -0.5V specified by manufacturer should be left for ground bouncing only.

Bye,
Kai