[time-nuts] Switching regulator replacement for 7805

Bob Camp kb8tq at n1k.org
Sun Dec 4 20:45:55 UTC 2016


Hi

Given that the parts to build one are fairly easy to get and that we likely have “nutty” 
EMI requirements. Maybe a small board that drops into a 78xx footprint is the 
better solution. 

Bob

> On Dec 4, 2016, at 3:39 PM, Adrian Godwin <artgodwin at gmail.com> wrote:
> 
> At Farnell, they're listed under Power Supplies rather than Switching
> Regulators (which is a subdivision of Semiconductors).
> 
> It makes sense since one is a board product and the other a chip, but when
> the board product is a drop-in replacement for a TO220, less sense!
> 
> 
> On Sun, Dec 4, 2016 at 7:44 PM, John Ackermann N8UR <jra at febo.com> wrote:
> 
>> And Digikey does stock the Murata part, for about $4.30.  Why I couldn't
>> find it when searching their site for switching regulators, I don't know.
>> 
>> John
>> ----
>> 
>> 
>> On 12/04/2016 02:39 PM, John Ackermann N8UR wrote:
>> 
>>> Thanks for that pointer!  When I searched Digikey, I wasn't able to find
>>> anything that was in the 3-lead TO-220 case.  I will definitely check
>>> out the Murata units, as I suspect they perform better than this one.
>>> 
>>> John
>>> ----
>>> On 12/04/2016 02:01 PM, Adrian Godwin wrote:
>>> 
>>>> Thanks for this. I've seen something similar from Murata :
>>>> 
>>>> http://uk.farnell.com/murata-power-solutions/oki-78sr-5-1-5-
>>>> w36-c/converter-dc-dc-1-o-p-7-5w-1-5a/dp/2102101
>>>> 
>>>> 
>>>> Since they're a mainstream supplier of inductors they may have managed
>>>> better performance - it would be interesting to compare.
>>>> 
>>>> 
>>>> On Sun, Dec 4, 2016 at 6:50 PM, 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!
>>>>> 
>>>>> John
>>>>> 
>>>>> 
>>>>> 
>>>>> 
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