Hi If your MCU has a POR that resets the internal oscillator that’s an unusual part. Most of them I’ve seen simply reset the CPU…..Once the 8 MHz crystal oscillator is running at 37 to 53 MHz (or KHz) it may or may not ever return to 8 MHz on it’s own. Yes, you need to get into some nutty (as in volt per second) rates to see a lot of this kind of thing. It’s not a common thing to run into on a real design and it is even less common to see it tested for. Unfortunately there are a few fields / companies where really slow supply ramps are “the way it’s done”. Needless to say, they have a lot of fun getting stuff to work right.
Bob > On Apr 13, 2017, at 1:41 PM, Scott Stobbe <[email protected]> wrote: > > I can't say I have run into that issue with a MCU as most 21st century ones > have a decent POR and Brown out detect (which typically burns 10x more > current than a 32k XO + RTC, and may get switched off in battery > applications, and then problems can occur). What does seem to come up is > stuff hanging off non-always on power rails (ADC,DAC,Sensors,etc), leakage > and back-feeding onto their dedicated supply has them try to startup on > leakage but there isn't enough leakage to actually power the device. They > may issue the on die reset once and then the supply collapses all the flops > lose their reset state, but the IC dosen't try to reset again. > > Fortunately, you can buy a bunch of LDOs which include a small discharge > FET to help this case as well as others. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
