On Mon, Jan 17, 2011 at 10:08 AM, Oli Glaser <oli.glaser@talktalk.net>wrote=
:

> That page is showing waveforms at a particular input voltage (of around
> 12V I think) so you can't really go from that unless you are doing
> exactly the same. At different input voltages/loads things will change.
>
> > * The plastic bag that the inductor came with says that it's a "power"
> > inductor rated at 1/2 W with a resistance of 0.3 ohms. I then measured
> the
> > resistance with my multimeter and found it to be 0.7 ohms, but that cou=
ld
> be
> > wrong?
> > * At 0.3 ohms, (I^2)*R<  0.5 W, I would get around 1.29 A max. What are
> the
> > effects of pushing more than 1.29 A through this thing?
> > * I don't plan on drawing more than 1 A, so the peak current through th=
e
> > inductor should be less than the waveform shown on page 26, and I shoul=
d
> be
> > good to go?
>
> Not necessarily (I think quite likely not)
> I can remember whether you are using this for buck/boost but I agree
> with Alan that looking at some app notes would be a good idea. Also I
> really recommend getting LTSpice if you have not already (great free
> simulator in general) and using their example setups to simulate.
> I just looked and they don't have the 3112 but they do have an example
> of the 3533 which is quite similar (in <install folder>/examples/jigs) -
> I think a lot would be gained from running this example and changing
> various parameters (input voltage, inductor series resistance etc) and
> watching the pulse width, inductor current, output current etc. For
> example what happens to the current when you have the in voltage lower
> than the out voltage and vice versa? What happens to the pulse width
> when in voltage is higher? What happens when you raise the  inductor
> series resistance? What happens when you change the load?
> This plus going over the theory thoroughly should help I think (i.e.
> don't just take the simulation results completely for granted - not
> always correct/comparable to real world conditions - e.g. sometimes
> totally wrong/misleading if set up the wrong way, although with the LT
> examples they *should* be set up okay at least to start with)
>
> Also, doing similar in the "real world" will be good learning too (i.e.
> just shove the inductor in and see what happens.. :-) )



Ok, I just ran the simulation. How do I get it to simulate more than 2 ms?

This is what it looks like:
http://img835.imageshack.us/img835/879/capturebx.png

Seems that the current through the inductor is a lot higher than 2.7 A.
--=20
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