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Looking for advice on selecting voltage regulators for a project

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Positron:
Hi,

I'm a bit of a newbie at electronics (I'm a software guy) so I'm looking for some advice on how to get the voltages I need for a circuit.

I'm building a circuit that needs a :

+5v supply  for digital logic (500ma to 600ma)
+/- 12v supply for audio opamps (50ma - 100ma)

I want the circuit to be powered by a 9v - 16v plug pack (whatever is lying about in the junk box)

I was think of using a LM2575 / LM2595 (or something similar) to get the 5v supply and then feeding that into a MAX743 to get the dual rail 12v supply.

I could also use a 7805 for the 5v supply, but they tend to get pretty hot even with a 9v supply so I'd like to avoid that.
I've used a MAX743 before and had no problems with it, but I've never used the LM2595, or two switchmode regulators together.

Could anyone tell me if this a sensible approach or if there's a better way to do it?

Rerouter:
seems like a decent design, however it will kinda fall back to what level of noise you can tolerate, at 52Khz on the LM2575, and 150Khz on the 95 you would probably want to filter its output :/

nctnico:
I'd go for two DC-DC converters. Nowadays they are pretty cheap.

Kremmen:
+1 for filtering the output.
Does the +/-12V need to be carefully regulated? If not, why not save 1 regulator and take both voltages from a single one? Of couse you need a transformer based topology for that but it might still be cheaper that 2 separate supplies.

Positron:

--- Quote from: Kremmen on April 22, 2012, 06:55:14 am ---+1 for filtering the output.
Does the +/-12V need to be carefully regulated? If not, why not save 1 regulator and take both voltages from a single one? Of couse you need a transformer based topology for that but it might still be cheaper that 2 separate supplies.

--- End quote ---

I've never worked with mains voltage before, I think it's also illegal where I live.  I'd rather keep it on a DC plugpack.  It does need to be regulated (although I guess you could use a LM317/337 for that.)


--- Quote ---I'd go for two DC-DC converters. Nowadays they are pretty cheap.
--- End quote ---
I had looked at DC-DC converters, you can even get dual rail ones.  Although the only place I could get them is from digikey/mouser that I've found.  I'll have to try to find a local supplier, as using one of those would reduce the parts count a lot.

I might be able to get access to a scope so I can make up some test circuits and play around with filtering.

Thanks for the responses!

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