Quote:
Originally Posted by Pdelcast
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
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Is it possible that having 2 Fet's tripping the overcurrent, meaning your sense resistor (via Fet) readings are not consistent and Isense is way to sensitive from IC to IC? I am assuming that it is 1 fet per IC (6pin, close to inductor).
Yes, 4 amps inductor is hard to find, but I thought that you can get openframe ones and direct solder them to pcb.