Exo

Does anyone know a place where i can get inductors that can be used with the LM2575 buck switcher? I need something in the range of 680µH (give or take a bit). @ 1Amp.

Also, inductors are rated for both DC and AC current. wich one applies to the LM2575? DC, cause it is Dc, or AC cause it switches ?

williB

do they have to be new?
cuz lately i have been finding a lot of junk pc monitors that have tubular inductors in them .. or maybe you could wind your own..

Exo

They don't have to be new, but i can't find any.

I have tons of old computer, tv, video, etc boards lying around, but no inductors of the required value and/or current.

They have to have a low series resistance too.

chemelec

Thats a Pretty High Inductance at that Current rating.

I would suggest getting a small Torroid core and winding your own Inductor with about a 20 AWG Wire.
Or I could Possibly make you one.

Or Alternately finding a Newer type Chip that operates at a Higher frequency and a Lower Inductance. There are a lot of chips now that use 10 uH to 50 uH Chokes.
And they are More Efficient.

Gary

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chemelec

According to My Data Book the Inductor is 330uH. If you send me an Email, I'll send you the Schematic as Printed in the 1993 National Data Book.[/img]

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Exo

It says 330µH in the 'typical application'

but lower in the datasheet is a inductor selection graph Vin Vs. Iout max.
my requirements put me on the 680µH line.

Also, if you can name some of those better replacement chips that would be nice.

fredsm

130 turns of AWG 28 magnet wire on a T-94-26 toroid
core should yield about 680 uH at a 1A rating.
Use AWG 24 for a 2A rating.
If you want to use a bobbin core, you will need about
the same number of turns on a B-77-1011 core.
<als>

chemelec

According to My Data Book, The 330 uH produces an output of "5 Volts at 1 Amp". Thats what you want, I Believe.

Typically A Higher Inductance Lower Frequency and results in Poorer Efficiency. Problem With Higher Frequencies is the Need for Faster Diodes.
Every Change in Parts has its Tradeoffs.

I'm on Slow Internet, so doing searching isn't my thing.
Most cases, I use Step up, Not Step down, SoI don't have a Specific Chip in mind.

Phone Texas Instruments at 1-800-336-5236 (My Favourite)

or Motorola at 1-800-635-8291 (Not Sure if this is a Current Number)

If you give them your requirements, they can help you.

Texas Instruments is also Extremely Helpful for Free Samples.
Motorola (On Semiconductor) also somewhat helpful for samples.

One Chip that I did use was an LT1271, but its rated at 4 Amps. It Worked VERY GOOD for both boost and Reduction. But NOT CHEAP.

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NickC84

I use 68uH inductors with the 2575, I got them from a HamFest for free lol. They work perfect, I don't know what to tell you about where to find them though they have the label ami/smd if that helps. Have fun!

Exo

Yes, i tried diffirent inductor values and they all work.

But in the datasheet there's a graph showing the relation between input voltage & output current and what inductor to use best.

I think it is meant to get the highest efficiency.