It may be in your interest to pick up the Maxim evaluation kit for this chip and compare their board layout to yours.
joshua On Wed, 28 Sep 2005, Timothy Miller wrote:
Here are images of the circuit diagram for the power supply circuit in question, courtesy of our friends at gitk.com: A scaled and rotated version: http://opengraphics.gitk.com/circuit_smaller.jpg The original full-size image: http://opengraphics.gitk.com/circuit.jpg The first image is probably most useful. We've spent about a week trying to get this to work without success. First, we built it on copper clad but quicky realised that was not going to work. Too much inductance in the high current carrying connections led to all sorts of voltage spikes that upset the MAX8578 IC. Then we built the circuit on a pre-existing blank circuit board with a design similar to this. We knew the power on the existing board was good, so we have a good idea that the layout is OK. We will provide a sketch of the PC board layout when we get the chance. The new build of the circuit worked OK until we started loading the circuit. When we attach a 0.5ohm load resistor, something in the MAX8578 IC trips, and shuts off the output. From then on, it continually tries to ramp up the output voltage (every 20ms or so) but the output only gets to about 1.5V before the MAX8678 trips again. We're running off a PC power supply, so there should be plenty of juice to go around. We've tried a couple of ICs, different FETs, setting the over-current protection really high and a few other things, but we get the same results. We've spoken to a couple of apps engineers at Maxim, but they haven't been able to figure out what we're doing wrong. (Written by Howard, edited by Tim.) _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
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