Current limit of TO220 LM317 is above 1.5A

Hi,
Please confirm that the current limit of LM317 (TO220) is not internally limited to 1.5A as the datasheet suggests?


We need 3A out of it for a few 100ms at a time.

The IC has internal over-current protection. Rated maximum load current is 1.5A minimum, 2.2A typical, but no higher figure is given. It's probable/possible that the over-current protection would kick in before 3A, even for a short overload period.
A well-designed circuit would not have components operating at or very close to their rated limits.

Thanks, the datasheet is unusual, because page 13, fig 17, suggests that the LM317 can carry 1.25V/0.2R = 6.25A.

LM317
https://www.ti.com/lit/ds/slvs044x/slvs044x.pdf

opampsmoker said:

Thanks, the datasheet is unusual, because page 13, fig 17, suggests that the LM317 can carry 1.25V/0.2R = 6.25A.

Click to expand...

Yes, that's an error in that data sheet..
The LM317 output current is indeed internally limited to 1.5A (min).

If you need more you can increase the current as shown by Figures 22 and 23 in the data sheet.

opampsmoker said:

We need 3A out of it for a few 100ms at a time.

Click to expand...

The device schematic suggests that the internal current limit is instantaneous, while the thermal limit is not.

Consider changing to the LM350. It is a drop-in replacement rated for 3 A continuous.

ak