I made a simple circuit to convert 13.5V to 5V in LTSpice.
I used step function to step through different load resistors from 1ohm to 10ohm in 0.2ohm increment.
The result shows that, the output voltage begin to drop when the load resistance is below 6 ohm or lower.
I then plotted the V load vs I load and found the V load begin to collapse when I load reaches 840mA.

From all the datasheet of LM317, I thought its maximum current output is 1.5A, what did I do wrong?
attached:

 

You likely did nothing wrong.
It depends upon the model you use.
Mine tops out at around 1.4A

 

hmm, interesting, the only differences are:

(1.4A top)
R26 32 3 .1
.MODEL QNL NPN(EG=1.22 BF=80 RB=100 CCS=1.5PF TF=.3NS TR=6NS CJE=2PF
+ CJC=1PF VAF=100)
.MODEL QPL PNP(BF=40 RB=20 TF=.6NS TR=10NS CJE=1.5PF CJC=1PF VAF=50)


VS

(0.8A top)
R26 32 3 .06
.MODEL QNL NPN(EG=1.22 BF=80 RB=100 CCS=1.5PF TF=.3NS TR=6NS CJE=2PF IS=6E-16
+ CJC=1PF VAF=100)
.MODEL QPL PNP(BF=40 RB=20 TF=.6NS TR=10NS CJE=1.5PF CJC=1PF VAF=50 IS=6E-16)

Thanks for the working .sub.

 

hi jii,
When you post an 'asc' file and a plot image, please make the asc file match the plot, so that we can compare exactly our results.
E

 

My bad. I didn't even realize I did so much modes and saves in a short time. I'll be more careful next time.

I played around the value for R26, it appears to be what's responsible of the output current cut off. A value of 0.0001 makes it drops off at 85A.

 

hi,
If you post your latest working asc file, I will give it a run.
E

 

hmm, interesting, the only differences are:

I believe you reversed the two models.
The one with the lower value for R26 should have the higher current limit.

 

Strange. When I run the post #1 asc file using the post #2 sub file I get this :


Edit: Ah, seems to be a pin order/name mismatch between the model and the symbol. Will have a play.
Edit 2: Sorted by editing symbol.

 

hi

I didn't try your model because it wasn't shared...but mine works ok.
Try lowering the set resistor (R1) to 240 and recalculate R2. I believe there needs to be at least 5ma flowing thu the set resistor for it to regulate properly.