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'[EE]: DC-DC converter woes?'
2003\03\01@171149 by PicDude

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part 1 1698 bytes content-type:text/plain; (decoded 7bit)

Any of you folks used the LM2588 switcher (or similar) before?  I've been
having probs w/this chip, so I whittled it down to a very small/simple
circuit now, but I still can't get it to work.  For this, I'm using a fresh
LM2588 (from a different order), so I doubt that the chip is at fault.

My circuit (see attached circuit, which was created with NS's SMS tool)...
==========
- Input is a 9V battery, and I have a 50-ohm load at the output.
- Transformer is a FT50-43 toroid core wound with 9 turns of 18-gauge wire
for the primary and 2 turns of 20-gauge wire for the secondary.
Schottky is a 1N5822.
- For voltage divider R1,R2 I'm using a 1.8k and a 3K.

My results...
==========
- Vout is 0V.  Bad.
- At the Vin terminal on the chip I get 9.1V.  Good.
- At the SW terminal (DMM set to DC Volts), I get 9.1V, and on AC Volts I
get 0V.  Not good....?
- The chip warms up very, very mildly.  Enough to know it's getting power,
but nothing to worry about.  (The last circuit I built with one of these
overheated till to the point of burning my finger and then smoked.)  But
this seems good.

I've tried switching the output winding polarity in case I accidentally got
that wrong, but that did not help any.

Unfortunately, no oscope with me here, so I really can't see what's
happening.  Anyone have thoughts on what may be wrong here?  The only thing
I I'm unsure about is if 2 turns on the toroid is enough.  Only other option
(that I have with me) is a T130-3 with 34 and 9 turns for pri/sec resp.

Cheers,
-Neil.






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part 2 9434 bytes content-type:image/gif; (decode)


part 3 2 bytes
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2003\03\01@172229 by Tal

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I have used LM2587T12.
Is it help you? do u need any info?

Tal


-----Original Message-----
From: pic microcontroller discussion list [.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU]On
Behalf Of PicDude
Sent: Sunday, March 02, 2003 12:10 AM
To: PICLISTspamKILLspamMITVMA.MIT.EDU
Subject: [EE]: DC-DC converter woes?


Any of you folks used the LM2588 switcher (or similar) before?  I've been
having probs w/this chip, so I whittled it down to a very small/simple
circuit now, but I still can't get it to work.  For this, I'm using a fresh
LM2588 (from a different order), so I doubt that the chip is at fault.

My circuit (see attached circuit, which was created with NS's SMS tool)...
==========
- Input is a 9V battery, and I have a 50-ohm load at the output.
- Transformer is a FT50-43 toroid core wound with 9 turns of 18-gauge wire
for the primary and 2 turns of 20-gauge wire for the secondary.
Schottky is a 1N5822.
- For voltage divider R1,R2 I'm using a 1.8k and a 3K.

My results...
==========
- Vout is 0V.  Bad.
- At the Vin terminal on the chip I get 9.1V.  Good.
- At the SW terminal (DMM set to DC Volts), I get 9.1V, and on AC Volts I
get 0V.  Not good....?
- The chip warms up very, very mildly.  Enough to know it's getting power,
but nothing to worry about.  (The last circuit I built with one of these
overheated till to the point of burning my finger and then smoked.)  But
this seems good.

I've tried switching the output winding polarity in case I accidentally got
that wrong, but that did not help any.

Unfortunately, no oscope with me here, so I really can't see what's
happening.  Anyone have thoughts on what may be wrong here?  The only thing
I I'm unsure about is if 2 turns on the toroid is enough.  Only other option
(that I have with me) is a T130-3 with 34 and 9 turns for pri/sec resp.

Cheers,
-Neil.






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2003\03\01@172845 by Dave Wheeler

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Hi Neil,

Silly question but why is pin 1 connected to ground. The data sheet
says floating for on and >3V for off.

Might be way off,

Dave

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2003\03\01@185333 by PicDude

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IIRC, only diff was a remote on/off capability, so sure --
I'd appreciate any help you can offer.

Thanks,
-Neil.




> {Original Message removed}

2003\03\01@185731 by Tal

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Did u get the PDF i have sent u?
is it help u?

Tal

-----Original Message-----
From: pic microcontroller discussion list [@spam@PICLISTKILLspamspamMITVMA.MIT.EDU]On
Behalf Of PicDude
Sent: Sunday, March 02, 2003 1:53 AM
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
Subject: Re: [EE]: DC-DC converter woes?


IIRC, only diff was a remote on/off capability, so sure --
I'd appreciate any help you can offer.

Thanks,
-Neil.




{Quote hidden}

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2003\03\01@190807 by PicDude

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Not silly.  First test was with it open, but I later tried
the ground since it IS an active-low signal.  According to
the schematic that SMS produces, it is connected thru a
resistor with a value of "TRUE".  But either way it did not
work.

Thanks,
-Neil




> {Original Message removed}

2003\03\01@191033 by PicDude

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I did get it.
It's almost the same circuit I'm using, except...
 - No remote switch.
 - No coil spike diodes (okay for my test ckt).
 - No voltage divider (I'm using the adj version.
 - Transformer.


The big questionable is the transformer, so I'm
tending to guess that that may be the problem.
What did you use for this?

Thanks,
-Neil.





> {Original Message removed}

2003\03\01@211105 by Larry Reynolds

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Pic Dude,

       The data sheet says very clearly on Page 23 to leave Pin 1 OPEN!  Do
not ground it, nor tie it to supply.  It CANNOT source or sink any
current!! You may need a new device....  :-((

Larry


PicDude wrote:
>
> Any of you folks used the LM2588 switcher (or similar) before?  I've been
> having probs w/this chip............

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