I'm working on my SBC's power design.

I plan on offering two power rails. One 5V and the other 3.3V. I have a need for both power voltages in my design.

I have built something similar to the attached schematic on a breadboard and it seems to work pretty well. At least according to my multi-meter.

I welcome any constructive criticism.

Thanks!

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Cat; the other white meat.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Other than Garth's comments about the LDO regulator's capacitors I see no reason why it shouldn't work.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Awesome!

Thanks for the recommendations. I will look at the datasheet and find the correct values.

Thanks!!


**EDIT**

I'm an idiot. It's right there in the datasheet. I've got to remember...it's ALWAYS in the datasheet.

I will update the design but it appears you need a 1uF cap on the OUT and a 1uF on the IN.

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Cat; the other white meat.

For best results, mount both caps as physically close to the regulator as possible.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Roger that. I also do the same with decoupling caps too.

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Cat; the other white meat.

Final version.

Opinions appreciated.

Thanks!

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Cat; the other white meat.

Just for grins, make C8 a 100µF cap instead of 10µF. The physical size difference will be minimal and you'll get a little better regulation from the 7805 as loads on the 5 volt circuit fluctuate.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Ah, good idea.

I have several 1000 uF caps. Do you think one of those should go on the switch?

I forgot to add the schematic for the switch so I should be able to update that soon.

Thanks


** EDIT **

Let me rephrase that...should there be a large cap supplying the "IN" pin of the 7805?

_________________
Cat; the other white meat.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

The 7805 doesn't need a large cap on the input, as long as the input voltage stays above 7V or so (exact value can be found in data sheet).

I will certainly put bypass caps on all IC's. Even the clock. Just because.

I think I might go ahead and put a cap on the 7805 input line. This isn't going to be a high-volume production so I'm not too concerned on saving a few cents here or there.

Thanks again for the input.

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Cat; the other white meat.

All depends on from where the 7805 is getting its juice. If the basic source is sufficiently filtered, I'd say don't bother, as the 7805 is fast enough to filter out a reasonable amount of ripple.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

More than likely, it would be from a 9V wall-wart that was regulated.

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Cat; the other white meat.

A cosmetic observation, but wouldn't the schematic be clearer if the GNDs were joined up? When I first glanced at the schematic I was a bit confused. I assume the two rails have a common ground; the net name is the same at both points. But for me this would look clearer if the grounds were joined with a wire.

What's the current draw? Don't forget the heat-sinks on those 78xx

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