Okay, now that I've killed a power supply, its time to get a professional opinion. I've been trying to track down why my sum gate (rev 2) consumes so much power. While poking around and checking how much power different components consume I saw ridiculous numbers like a 393 comparator pulling over 400 mA, then suddenly changing to around 130 mA, then jumping up to 200 mA. That's just one example. I even tried swapping out IC's to make sure it wasn't a bad component. While checking this all out I detected a faint burning smell (uh oh) and quickly confirmed that every component on the board and my DC/DC converter were cool to the touch. No dice; it was the wall wart giving up the ghost.
My components are as seen in the SumRev2.pdf file and my DC/DC converter is this little module. My +5v, GND, and -5v lines come directly from its outputs. I've also got two simple resistor dividers providing the -1v and +1v references, but I'm sure that isn't the problem because they are only used for high impedance comparator inputs. Does anybody see anything in my schematic that would explain the crazy power consumption? Thanks much if you can help!
Oh yeah. I tried adding all the appropriate bypass caps (not shown in the schematic) out of a primitive urge to perform a magic ritual where knowledge was lacking. As expected, it didn't work.
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Actually, I did eventually figure it out. It turns out that some old-school comparators (the LM393 specifically) require a bit of positive feedback to prevent high-frequency oscillation. This in combination with some poor power management practices on the analog switch IC appear to be the culprits. After reading a few app notes and adding appropriate passives I haven't seen a repeat of the problem yet. It was just the kind of problems you run into when you have lots of theoretical knowledge but little practical experience.
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have you considered asking another Hackaday person for assistance? I know of another who is working on a Ternary project, try them.
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