lm317ltspice
I built the following circuit in LTSpice using LM317.
With a current load at the output, stepping from 0.1A to 1A, I noticed the output voltage collapsed at around 800mA.
This is a surprise, since I read the datasheet somewhere that LM317 has a maximum output current of 1.5A.
So what did I do wrong in the simulation?
I think that you are dissipating too much power into the potentiometer. My calculation works out to 161mW when the total resistance is used. If it is a low power 200mW version, it might be too much. Swap R5 for a 1K or 910 ohm and do the experiment with the 5V again and see how it varies.
Since I cannot easily post images in comments... "there's your problem" as the Hyneman would say.
The voltage drop across Rs is only guaranteed if certain conditions are met:
In this case the first condition wasn't met.
Best Answer
Turns out it was the model I used had a cut off at 840mA.
After I tried a LM317.SUB from someone else, it started to cut off at around 1.4A.
The "working" .sub file has the following changes than the one I previously used:
Note, the smaller R26, the higher the cut off current it will get.