ADC IN MSP430G2553

The maximum voltage you can apply to a portpin depends on the supply of your micro. 3.6V is the maximum recommended voltage which is for the whole device, including the supply voltage. The device gives you some additional space up to 4.1V as the absolute maximum rating before the microcontroller can take permanent damage. The maximum voltage you should give to a pin is the voltage you are using as supply (plus 0.3V due to internal protection diodes). If your supply is 3.3V for example, then you should only give 3.3V on any pin. If you exceed this 3.3V plus the additional 0.3V of the internal diode, current starts to flow into that pin. The current damages your micro, not the voltage. The internal diodes can handle a maximum of +/-2mA. If you apply a higher voltage than the supply voltage and you limit the current with a resistor to be below 2mA, it's OK and will not damage the device.

So if you want to measure 5V you have to limit the current. But I don't see any sense in that - you are writing ADC in your title and if you apply 5V (with a resistor) your ADC result will give you 0x3FF for all voltages over your selected reference voltage (1.5V or 2.5V if you use the internal reference).

If your signal varies up to 5V and you want to measure all of it you should use a resistor-divider to scale your maximum input voltage down. Use two identical resistors to bring the 5V down to 2.5V, for example.

Dennis