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I'm building a device that will have STM32F750, and now thinking about stability in case if power or software will misbehave. As per topic - is it worth it to have an external voltage monitor and watchdog (Diodes Inc. APX823, for example)?

Obviously, STM32 has internal POR and watchdog (independent from main clock) - but will these two cover all the corner cases? Any suggestions?

Some technical details:

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  • \$\begingroup\$ Well, an external watchdog is immune to you messing up your code and has more flexibility. So...it depends... It would help to know what this device is...like a robot or just a datalogger or whether it has coprocessors or whatever. \$\endgroup\$ – DKNguyen Mar 21 '20 at 19:59
  • \$\begingroup\$ @DKNguyen, STM32 is the only CPU, other peripheral reset lines are driven from it. It's an audio device with WM8985 codec, supposed to be always powered from USB (PC or dedicated power supply). USB input has some protection circuitry before LDO. \$\endgroup\$ – Andrejs Cainikovs Mar 21 '20 at 20:05
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    \$\begingroup\$ Probably not worth it then. \$\endgroup\$ – DKNguyen Mar 21 '20 at 20:06
  • \$\begingroup\$ @DKNguyen, thanks! Please add your comment as an answer and motivate, I'll mark it as accepted. \$\endgroup\$ – Andrejs Cainikovs Mar 22 '20 at 21:18
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Well, an external watchdog is immune to you messing up your code and has more flexibility. An external watchdog is also more suited for a system with multiple processors/FPGAs that might need to be under the purview of a single watchdog.

So...it depends...Usually for simple systems or system where safety or catastrophic failure is not an issue, an external watchdog is not worth it. For example, if your MP3 player freezes nothing bad really happens. But if the inertial measurement on your UAV stalls...that's kind of a really big problem.

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