> At 80C, the output will be 919mV.  (The datasheet doesn't give a
> specific number for 50C

Matthew, the datasheet equation will give you the 50C figure

For example, d/s states 80C -> 0.919V

V = (-3.88 * 10-6 * (80*80)) + (-1.15 * 10-2 * 80) + 1.8639

= (-0.024832) + (-0.92) + 1.8639

= 0.919068V

So, before crunching resistor numbers, 50C -> 1.2792V

> How do I approach building a voltage divider to provide me with these
> voltage references? How do I select the best order-of-magnitude for the
> resistors? What other considerations do I need to pay attention to?

The accuracy of the sensor and accuracy and drift of the resistors and
their voltage source. 1% metal film resistors are cheap enough, can't do
too much about the sensor. Presumably the sensor is the only device
exposed to the temperature variations. If the voltage regulator and PIC
are too, then there's a problem that needs solving

> Another potential topic: what are the pro's and con's of the LM20
> versus a NTC thermistor for this application? The thermistor seems
> to require more calibration and interpolation to correct for nonlinearities.

I recall some people have reported very good results with thermistors
despite that

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