[time-nuts] Switching regulator replacement for 7805

Attila Kinali attila at kinali.ch
Sun Dec 4 14:20:51 EST 2016

On Sun, 4 Dec 2016 13:50:21 -0500
John Ackermann N8UR <jra at febo.com> wrote:

> I found a cute little switching regulator that's a drop-in replacement 
> for an LM7805: http://www.ebay.com/itm/261243604047
> I got a couple to play with, mainly to see how bad the noise would be. 
> Here are spectrum analyzer and PN shots comparing a cheap surplus OCXO 
> when driven by a regular 7805 and by the switching replacement.
> The switching frequency is supposed to be 2 MHz but you can see that 
> it's more like 2.4 MHz.  Whether this performance is sufficient for any 
> application is up to you.  It sure runs a lot cooler than a 7805, though!

Cool! Thanks a lot! I wondered quite some time how much worse these
things would be. Did you also do some EMI measurements? 
For what is worth, the spectrum below 1MHz looks pretty decent,
especially considering how badly done the layout on those boards
are. They must have completely ignored the layout guidelines in
the datasheet.. :-/

If you have the time and leasure, it would be nice if you could
compare them to the OKI-78SR series from Murata. I would suspect
they perform quite a bit better on noise and EMI...beside being
cheaper and easier to source :-)

			Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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