LM78L05 at 18V

[Bio77]

Anybody ever use a 78L05 to regulate 18V down to 5V?  Data sheet says the maximum is 35V but the data sheet is generalized for the whole 78L series so I'm wondering.  I'd like to add relay switching to an 18V build.

[BricksnBeatles]

Should be fine, but you may want a heatsink. I can't remember how to calculate the heatsink requirements for vregs, but yeah.

[benny_profane]

The TI data sheet has an LM78L05 section with characteristics for test conditions of 7-20V. The Vin_max figure does seem to apply to all LM78L## devices. Current and heat may be concerns, but 18v in should be fine. You could always put a divider or other step down before the input.

https://www.ti.com/lit/ds/symlink/lm78l.pdf

[Bio77]

Voltage divider!  Why didn't I think of that 

Thanks, guys!  Much appreciated.

[Govmnt_Lacky]

Remember that heat is generated by current draw. The LM-series (I believe) is rated to about 1-1.5A. If your circuit is going to be drawing less than 100mA then there should be nothing to really worry about. If you are pulling close to the max then it may be a concern.

[danfrank]

Dissipation of the regulator is voltage drop within regulator (Vin -Vout) X current going through regulator. So, if the regulator is dropping a lot of voltage and pulling close to 100ma the L reg may get excessively warm. You can always get se a standard TO220 version, they don't take up much more space than an L version