[time-nuts] Switching regulator replacement for 7805
John Ackermann N8UR
jra at febo.com
Sun Dec 4 15:14:39 EST 2016
That's a very good point... the design I'm testing the regulator in has
a fair bit of C filtering, but no series L.
On 12/04/2016 02:45 PM, Chris Albertson wrote:
> Surprisingly good as a drop-in replacement.
> Question: Suppose you are doing a new design and had space on the PCB for
> one more small passive part. I wonder how the performance of the switcher
> with an LC filter compares with the 7805. Yes, I think this is fair. It
> is a trade off, It costs me one more inductor but I gain hugely reduced
> power consumption and heat.
> Or stated another way: You have shown the noise difference for drop in to
> existing circuit. What about two roughly equivalent new design circuits?
> How much to we pay in dollars and complexity to get equivalent noise?
> Thanks a lot for this work. Headed over to eBay right now....
> (My application uses LiPo battery and needs to have stable voltage as the
> battery drains but my current solution is noisyand those 78xx chips waste
> far to much power. )
> On Sun, Dec 4, 2016 at 10:50 AM, 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!
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