LM317L VS TL431




Give me an example where you'd use / prefer to use ONE over the other?...

..download the datasheets - there are examples in it.. :wink:

I looked at the data sheets

The TL431 prevents the output from going to a voltage too high for the "adjustable zener".
The LM317 prevents the output from going too low.
They have opposite functions. A load pulling current down from a TL 431 will not have a regulated voltage, but an LM317 will regulate the voltage when a load pulls a current down from the output. The TL431 is a negative regulator. The LM317 is a positive regulator. Neither one will set a voltage source which keeps a steady voltage when the load pulls up and down from the desired voltage.