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azjc
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05.26.2008, 01:41 PM

Quote:
Originally Posted by Pdelcast View Post
The ceramics show about .005 ohm or so. The inductor isn't as compact as the capacitors because there isn't any inductors as compact as the capacitors -- not really sure what you mean. The smallest 22uh 4 amp inductors are at least 10mm square.

The FETs are snubbed using an RC snubber -- to prevent ringing.

The component that is failing is the switcher controller -- a National LM3485. National is looking into it with us -- seems the overcurrent circuit is failing internal to the LM3485, and leaving the chip in constant overcurrent state. That's why the output voltage drops to 1.08V - -it's in hiccup overcurrent mode. Replace the LM3485, and all works well again.

Patrick

for the techies
http://www.national.com/pf/LM/LM3485.html
   
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