I have now three smartphones (SGS3 [neo], max 77686 or so) lying around, all more or less dead due to a broken voltage regulator. Since I am not a fan of coincidences, I suspect a broken wall wart somewhere around in my apartment, but I not only have too many to just throw them all away, I also currently don't have a scope to measure things.
Since I am suspecting transient too-high voltages that destroyed the S3s regulator, I want to build a simple circuit that can detect those. For normal DC (or rather low frequency AC) I can come up with some ideas (monoflop, comparators, zener etc.) that can be the base of a circuit, but I have no idea about how fast the transient can be.
Since those are all smpss, I think their working frequency is at most 200kHz so the voltages to detect should probably be in that timing area. I don't have much experience in what circuits would be a good idea to detect the voltages that I am searching for fast enough.
So what would be a good design idea for a circuit that detects, lets say anything above 5.5V that lasts at least 5µs (or if you have experiences with mentioned voltage regulators smaller times when they are likely to damage the regulator circuit)? Although it is sylvester soon and everyone appreciates some blowing up tantalum capacitors due to overvoltage, I would prefer something reusable with not too much components, that is also nothing that requires a microcontroller or similar.