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

Tal


-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On
Behalf Of PicDude
Sent: Sunday, March 02, 2003 12:10 AM
To: PICLIST@MITVMA.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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