FWIW, you can snub the switch node to dampen parasitic ringing in exchange
of a loss in efficiency of a couple percent. I'm pretty sure I have seen
this outlined in a few app notes.
On Mon, Dec 5, 2016 at 1:22 PM, jimlux wrote:
> On 12/5/16 9:13 AM, Dan Kemppainen wrote:
>
>>
>>
>>> Depending on
On 12/5/16 9:13 AM, Dan Kemppainen wrote:
Depending on the application, another possible application is to
sync up the DC/DC converter to the "main" clock source. This makes
the switching noise then coherent to the system, which either makes
it average out completely, or possible to filter it
Depending on the application, another possible application is to
sync up the DC/DC converter to the "main" clock source. This makes
the switching noise then coherent to the system, which either makes
it average out completely, or possible to filter it out in the digital
domain using a deep notc
On 12/5/2016 12:00 PM, time-nuts-requ...@febo.com wrote:
This is exactly the PWM to PFM mode switch I described earlier.
The 850mA are probably high enough that the DC/DC converter works
in PWM mode, thus switching with a constant frequency, even if the
load changes. On the other hand 200mA of
a surface mount oriented factory, but these
are becoming antiques.
Bob L.
> Sent: Sunday, December 04, 2016 at 8:07 PM
> From: jimlux
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Switching regulator replacement for 7805
>
> ... The other thing is that SMD inducto
urement"
>
> Subject: [time-nuts] Switching regulator replacement for 7805
>
> 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 th
Hi
The BLM18 gives you 300 ohms at zero current. It’s impedance at
zero current per the data sheet. If you look at other parts of similar
size, the impedance drops to nearly zero at the “rated current”. Great
if you have a signal lead and no current. Not so great if you have an
OCXO that is pull
Attila - I certainly do not differentiate between "ferrite bead" and "single
turn toroidal choke".
I think the SMT inductor manufacturers think of them in the same bucket too.
what I think of as a "ferrite core for winding a multi turn inductor on", is
invariably listed as a "ferrite bead" in t
On Sun, 4 Dec 2016 17:07:53 -0800
jimlux wrote:
> > Wouldn't it be better to use a ferrite bead instead, for this application?
> > The much lower series capacitance and thus higher self-resonance frequency
> > should help damping the spurs.
> >
> sure, if you can get enough L. The other thing is
Well a sigma-delta modulator in loose terms is an error amplifier around a
quantizer, so you get 1/loopgain rejection of quantization noise (in other
words the noise is shaped out in frequency). Resulting in a noise spectrum
that converges in 1/N versus 1/sqrt(N) for flat Gaussian noise, versus
lob
On 12/4/16 2:59 PM, Attila Kinali wrote:
On Sun, 4 Dec 2016 13:28:44 -0800
jimlux wrote:
I little series L and another C (so you have a pi low pass) can make a
huge difference. If the load current is reasonably constant, then the
drop across the series R of the L will be constant, so you can
On Sun, 4 Dec 2016 16:41:13 -0500
John Ackermann N8UR wrote:
> The little OCXO I used for testing goes from about 850ma cold to 200ma
> hot (at 5V) and I noticed a very different appearance of the spectrum as
> the current dropped -- at high current, the switching spurs were quite
> narrow, bu
On Sun, 4 Dec 2016 13:28:44 -0800
jimlux wrote:
> I little series L and another C (so you have a pi low pass) can make a
> huge difference. If the load current is reasonably constant, then the
> drop across the series R of the L will be constant, so you can bump the
> dc/dc output to compensa
On Sun, 4 Dec 2016 16:22:02 -0500
Scott Stobbe wrote:
> If you wanted to be nutty you wouldn't go PWM at all, just like
> fractional-N sythns don't just mash 2 divider values. You would sigma-delta
> modulate your power stage. I don't know if you can buy one COTS, but there
> are plenty of papers
Hi
I doubt that there is a significant demand for 10 ma output switchers. The
benefit of going from 12V to 2V as a switcher compared to linear is mighty
small. As a guess, I’d say that anything much under a watt is not worth doing
in this arena. That gets you up to at least 100 ma at the normal
On 12/04/2016 04:34 PM, jimlux wrote:
Even for time-nuts, I suspect we're not looking to eke out the last
percent of efficiency from 96% to 97%, or handle wildly varying loads,
etc. Nor are we usually looking for absolute minimum parts cost.
The little OCXO I used for testing goes from about
On 12/4/16 1:09 PM, Attila Kinali wrote:
On Sun, 4 Dec 2016 15:45:55 -0500
Bob Camp wrote:
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.
I don't fully ag
On 12/4/16 12:14 PM, John Ackermann N8UR wrote:
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.
I little series L and another C (so you have a pi low pass) can make a
huge difference. If the load current is reasonably consta
If you wanted to be nutty you wouldn't go PWM at all, just like
fractional-N sythns don't just mash 2 divider values. You would sigma-delta
modulate your power stage. I don't know if you can buy one COTS, but there
are plenty of papers on rolling your own.
On Sun, Dec 4, 2016 at 4:09 PM, Attila Ki
On Sun, 4 Dec 2016 15:45:55 -0500
Bob Camp wrote:
> 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.
I don't fully agree. To go full "nutty" you would
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 wrote:
>
> At Farnell, they're listed under Power Suppl
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
Hi
The most common thing to miss on decoupling a switcher is that both the output
*and* the input will generate crud that sprays all over the place. Series L on
both
the input and output are a really good idea. Microhenry (as opposed to
milihenry)
chokes are generally good enough. Values are
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 sma
On 12/4/16 11:45 AM, 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
On 12/4/16 11:39 AM, 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.
The Cui parts are also available
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
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
In message <5844656d.5010...@febo.com>, John Ackermann N8UR writes:
>I found a cute little switching regulator that's a drop-in replacement
>for an LM7805: http://www.ebay.com/itm/261243604047
Traco has had the TSN and TSR series for some years now, and they
perform nicely in all applic
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
On 12/4/16 10:50 AM, John Ackermann N8UR 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 ch
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, 4 Dec 2016 13:50:21 -0500
John Ackermann N8UR 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 an
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