Sandman101

Ante, My setup requires the protection to be "resetable" .. as in not a fuse blown but just protection that won't stop the system from running. Also, is this setup applicable to a DIO line? The circuit shown is for a power supply... (my thanks to everyone who has been replying!!)

Would an MOV protect the line if the +28V was applied in a long-term sense, as in, indefinite protection? I'm not looking for spike protection, but a user mistakingly setting the pin to 28V without good monitoring (ie, it's left on long-term). Is an MOV going to cut it?

By resistor and zener you mean: DIO ---/\/\/--------- DIO OUT | ---- / \ | | GND I choose a zener with zener voltage equal to the DIO voltage level .. but what about the resistor ... isn't the resistor going to cause a voltage drop? what is an ideal value for a 3.3V level ? Thanks for the help!

Hey all, It's been a long time since I've done discrete electronics and I'm in need of a discrete solution (with logic gates): I have a switch, that once opened, a circuit is "turned on" and runs. If the switch closes, it cannot affect the system. Sorta like an alarm .. when you break in, the alarm shouldn't shut off once the door has been closed ! Any help is appreciated! Thanks!

Greetings, I have a design question at hand: I have a group of DIO lines, attached to an FPGA, running +3.3V signal levels. Obviously I would like to drive the signals with buffers, which is simple enough. The problem is the outside world of this device has the probability of pulling the DIO lines up to +28V (this would be an accident, not a common occurance). I've been searching for SMT or BGA solutions to this problem (ie. a buffer with this much protection on the output side) and have found none. If, by chance, anyone knows of any ICs that are capable of such a feat, I would greatly appreciate it. In the event no one knows of any individual ICs that would accomplish this task, a discrete component solution will have to do. If anyone has any recommendations, perhaps even an example schematic, it would be appreciated (using Zeners, resistor networks, etc.) thanks for any help!