I have a circuit that has a heavy-duty 5V regulator (LM340K-5.0 to be precise, the LM309K is probably an equivalent).

As I'm considering reproducing / simplifying the original, I've hit a stumbling block with the regulator. Seems all the reputable sources (Digi-Key et al) all want to charge over $50 for ONE, and which makes the project unfeasible... I see some are available for less than $10, but I don't want to get rooked with a possibly counterfeit part.

I don't know for sure yet exactly much regulator I DO need (but two 12V supplies exist on the board, presenting a possibility of splitting the 5V load), but just wanted to see if anyone else ran into this and what, if any, solution they chose.

Thoughts?

 

Get a smps module that can take 12VDC input and be set to 5v output. Handle up to 5 amps. 80 to 90% efficient so little heat.

The linear LM350 uses a method to simply convert the excess voltage x drawn current to heat. Essentially 0% efficient.

 

Something like this - I can send you a breakout board to make this a 5v 3-pin device like the other...
https://www.digikey.com/en/products/detail/murata-power-solutions-inc/OKR-T-6-W12-C/2199629

 

That part should work out fine, and price is VERY reasonable. Appreciate the suggestion.

I'm down to picking out footprints for the last few parts (using KiCAD) so I could just drop that right into the schematic and free up the space the heatsink would consume otherwise. I may be interested in the breakout board regardless.

Relevant portion of schematic attached (with the LM340K-5 still present)

 

You'll need to connect the voltage programming pin to ground with the correct resistor to get a 5v output. See the last page of the datasheet. Or, I can tack it in place if you need a 0.1" offset breakout board.

 

Actually, what about something like this? https://www.digikey.com/en/products/detail/cui-inc/V7805-1500R/2352143

Like I said, I'm laying out a new board based on that portion of the board that's actually in use, so I'm not really constrained by the TO-3 pad layout at this point.

 

It has a maximum of 1.5A. If that is enough, it is a perfectly fine option.

 

My GOTO PLACE https://www.utsource.net/sch/LM340K-5.html has them.

 

I settled on the mini switcher regulator instead of staying with the LM309K / LM340K-5.0 for total cost, design, and construction considerations.

Barring any layout adjustments, I think this can move into the "parts to be ordered" column.