is it possible to use ADC10 with a 5V reference?

Steven Mills said:

I have a sensor that outputs 5V when it is saturated. Is there a way I can make it work with the MSP430?

YOu can use 2.5V reference and a 2:1 voltage divider (two identical resistors in series between sensor output and GND, and the MSP ADC input tied to their middle point)
yes, it is a waste of power, but since the MSPs input impedance is rather high, you can use two high-ohm resistors.

Alternatively, you can use an OpAmp to further increase the impedance (you still need the divider, since a single OpAmp cannot reduce the output voltage without inverting it, so you still have to reduce the input voltage)
There are OpAmps with several MOhm input impedance or even higher. So the voltage divider won't consume any noticeable energy. However, this adds offset and gain errors of the OpAmp to your signal, and the OpAmp needs some operating current too. And costs space and money.

If you oly need to quantize the sensor output (no need for a 'real' ADC, jsu tto see whether it is in the lower, middle or upper range), there may be other solutions too. Including a FET transistor that is switched on by an MSP pin, so the divider resistors are nto connected to GND (and don't act as a load) when teh MSP is not sampling the voltage. However, this again adds significant distortion to the signal (gain and offset and even nonlinearity)

Hello Steven,

I am not an expert like other users on this forum but I can see some solutions for you.

1. Use the transistor- simple, fast and cheap. 

2. Use operational amplifiers. There is a some methods (more or less complicated). It is possible to use operational amplifier in differential mode (like here: http://www.bcae1.com/opamp.htm). When you check only the state (high/ low) it is too complicated solution.

3. You don' t need to provide to MSP430 much current so you can choose bigger resistor values.

4. Use 2/ 3 diodes. Every diode has a forward voltage drop. I don' t recommend it  in this application (diodes have different voltage drop dependent on current, temperature and it is not linear for low current).

Steven Mills said:

I see that the voltage applied to any pin should not exceed Vcc +/- 0.3V and Vcc max is 4.1 V.

I can also advice you to do not use maximum specified values. On the whole, 3.6V is maximum voltage providing to MSP430. Besides of damage risk, I think, power consumption is also higher.

Edit.

Oh, I haven't read the title.

The first method isn't recommended in this case.