Regarding my prototyped circuit:
I presently have a 16VDC supply connected to power op amps. A 3VDC rail is needed at 100mA for an on-board microporcessor.
I am using a TO-92, 3V LDO regulator. It gets hot, which is doubly bad since this is a battery powered circuit.
What is the preferred method to make available these two voltages, with minimum loss in heat and curent?
Thank you for any suggestions.
Lou Yates
You need a switching regulator. A linear regulator in your situation is dissipating 4 times the power of the load.
Search for "point of load", "drop in replacement"
Start from there. That's a pretty big one though, and the wrong voltage too but it's just an example.
You might also design your own, it's pretty easy these days:
Of course more effort is needed.
You also need to make sure the extra electrical noise created by the switcher won't be an issue, and the extra size.
You are burning 16V-3V @ 100mA -> 1.3W. That's why it is getting hot. LDO means "Low Drop Out" but that just means it can work with a low difference between input and output, but you have 13V difference.
Use a switching regulator. For that requirements 16V in, 3V out, 100mA there are hundreds.
-- Reinhardt Behm, Bodenheim, Germany, reinhardt.behm@t-online.de
The National Semiconductor LM5009 handles your requirements at 85% efficiency, meaning it draws (3V x 0.1A)/0.85=3D350mW from your battery to supply 300mW to the load. The difference, 50mW, is dissipated in the regulator. The MSOP MUA package has a thermal resistance of 200oC/ W for a 200 x 0.05=3D10oC temp rise, and that assumes all power is consumed in the IC when a good fraction will be dissipated in the external diode.
do you have board space for this?
Take your pick, if you don't have room on an exiting board, you can always put a vertical board in there with 3 stabs to use existing To-92 holes. But a switching buck is a good place to start.
The incoming voltage is too high, too much R in the reg and it's heating up. a switching regulator would work out nicely for you
You could try an inexpensive switcher like this one:
Best regards, Spehro Pefhany
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