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From: dagmargoodboat on 12 Apr 2010 19:44
On Apr 12, 10:10 am, Joerg <inva...(a)invalid.invalid> wrote:
> Hello Folks,
>
> Got an inductor that someone has seriously underrated for saturation
> current, the 176uH version of this one, footprint S2 (0.394" pad distance):
>
> http://www.alfamag.com/PDF/InductorsChokes/Power%20Inductors%20&%20Ch...

That's only rated for 300mA. Yuck.

> Found this one that we could probably cram on there and at 220uH/1A it's
> already more than twice as sturdy:
>
> http://www.yuden.co.jp/ut/product/pdf/enr1_e.pdf

A 10mm inductor, 1A i_sat, 800mA i_dc. Used at 1.5A--past i_sat--it's
only ~140uH.

Are you sure you wouldn't rather use a 12mm inductor?

This 12mm 270uH part handles 1.2A rms, i_sat = 1.6A. Cheap. In stock
at DigiKey.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SRR1280-271KLTR-ND

> Since the current peaks in the converter will be up to 1.5A it'll still
> be a squeeze. Does anyone know an inductor series that fits the
> footprint dimensions but has even more oomph? Can be taller, height is
> not much of an issue. Shielded would be nice but we may not have a
> choice here. The exact inductance doesn't matter either as long as it's
> above 175uH.

Total energy storage (L * i^2 / 2), goes roughly with volume. If you
want to store more i^2, you'll need a bigger inductor.

SMD parts don't get all that tall, otherwise they'd snap or shear off.

Or, you could stack up two in series....?

--
Cheers,
James Arthur
From: Joerg on 12 Apr 2010 21:00
dagmargoodboat(a)yahoo.com wrote:
> On Apr 12, 10:10 am, Joerg <inva...(a)invalid.invalid> wrote:
>> Hello Folks,
>>
>> Got an inductor that someone has seriously underrated for saturation
>> current, the 176uH version of this one, footprint S2 (0.394" pad distance):
>>
>> http://www.alfamag.com/PDF/InductorsChokes/Power%20Inductors%20&%20Ch...
>
> That's only rated for 300mA. Yuck.
>
>> Found this one that we could probably cram on there and at 220uH/1A it's
>> already more than twice as sturdy:
>>
>> http://www.yuden.co.jp/ut/product/pdf/enr1_e.pdf
>
> A 10mm inductor, 1A i_sat, 800mA i_dc. Used at 1.5A--past i_sat--it's
> only ~140uH.
>

I am afradid its worse. Idc1 is 1000mA and they say in the footnote that
is the point where the inductance is down by 30%, meaning 154uH left.
What happens past that point would be unknown.


> Are you sure you wouldn't rather use a 12mm inductor?
>
> This 12mm 270uH part handles 1.2A rms, i_sat = 1.6A. Cheap. In stock
> at DigiKey.
>
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SRR1280-271KLTR-ND
>

Can't, no re-layout passible on this one.


>> Since the current peaks in the converter will be up to 1.5A it'll still
>> be a squeeze. Does anyone know an inductor series that fits the
>> footprint dimensions but has even more oomph? Can be taller, height is
>> not much of an issue. Shielded would be nice but we may not have a
>> choice here. The exact inductance doesn't matter either as long as it's
>> above 175uH.
>
> Total energy storage (L * i^2 / 2), goes roughly with volume. If you
> want to store more i^2, you'll need a bigger inductor.
>
> SMD parts don't get all that tall, otherwise they'd snap or shear off.
>

Well, a cube would be 10mm by 10mm by 10mm and cubes are stable enough.
That would be twice as high as this inductor is. I was hoping someone
would know a cube inductor.


> Or, you could stack up two in series....?
>

:-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: dagmargoodboat on 12 Apr 2010 22:15
On Apr 12, 8:00 pm, Joerg <inva...(a)invalid.invalid> wrote:
> dagmargoodb...(a)yahoo.com wrote:
> > On Apr 12, 10:10 am, Joerg <inva...(a)invalid.invalid> wrote:
> >> Hello Folks,
>
> >> Got an inductor that someone has seriously underrated for saturation
> >> current, the 176uH version of this one, footprint S2 (0.394" pad distance):
>
> >>http://www.alfamag.com/PDF/InductorsChokes/Power%20Inductors%20&%20Ch....
>
> > That's only rated for 300mA.  Yuck.
>
> >> Found this one that we could probably cram on there and at 220uH/1A it's
> >> already more than twice as sturdy:
>
> >>http://www.yuden.co.jp/ut/product/pdf/enr1_e.pdf
>
> > A 10mm inductor, 1A i(sat), 800mA i(dc).  Used at 1.5A -- past i(sat) -- it's
> > only ~140uH.
>
> I am afradid its worse. Idc1 is 1000mA and they say in the footnote that
> is the point where the inductance is down by 30%, meaning 154uH left.
> What happens past that point would be unknown.
>
> > Are you sure you wouldn't rather use a 12mm inductor?
>
> > This 12mm 270uH part handles 1.2A rms, i_sat = 1.6A.  Cheap.  In stock
> > at DigiKey.
>
> >http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SRR1....
>
> Can't, no re-layout passible on this one.

I'd hoped the 12mm unit might squeeze in the same spot, or maybe you
could make an adapter board. Yucky, but we've all had to do it.


> >> Since the current peaks in the converter will be up to 1.5A it'll still
> >> be a squeeze. Does anyone know an inductor series that fits the
> >> footprint dimensions but has even more oomph? Can be taller, height is
> >> not much of an issue. Shielded would be nice but we may not have a
> >> choice here. The exact inductance doesn't matter either as long as it's
> >> above 175uH.
>
> > Total energy storage (L * i^2 / 2), goes roughly with volume.  If you
> > want to store more i^2, you'll need a bigger inductor.
>
> > SMD parts don't get all that tall, otherwise they'd snap or shear off.
>
> Well, a cube would be 10mm by 10mm by 10mm and cubes are stable enough.
> That would be twice as high as this inductor is. I was hoping someone
> would know a cube inductor.

That's roughly what you'll need -- 1,000mm^3.


--
Cheers,
James Arthur
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