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TMS570LC4357: Does Hercules require use of EXTERNAL HARDWARE WATCHDOGS

Part Number: TMS570LC4357
Other Parts Discussed in Thread: TPS3431

From prior projects, any safety related application with a microcontroller , we would use a HARDWARE WATCHDOG ..like a TPS3431...we would "kick the dog" in SW from the uP(send a pulse out from uP to WD)...if the WD chip didnt get kicked , we'd shut down everything...the thought being Hardware trumps software for safety apps, 

does the Hercules have a HW watchdog embedded in it?...I know all uP have a SW watchdog embedded, where you upload or reset a register every so often to keep the processor going....but again, this is internal and is a SW thing...

in the qualifications of the Hercules, does it actually negate the use of such a HW device for monitoring?  (i.e. is it qualified without such HW monitoring)...

we also would use a similar approach for power....(hardware monitors power...if power dips/drops on one/several lines, shut things down)...

does the Hercules have a voltage level HW watchdog embedded in it?...

I see that the TPS65381 is designed specifically for use with the hercules and has all the hardware watchdogs in it....am I correct in saying this TPS65381 is HARDWARE watchdogs/monitoring?

  • Hello,

    For achieving the target functional safety integrity level an external watchdog may be mandatory, regardless of the capability of the on-chip watchdog. This is mainly due to common-cause dependencies such as clock sources, etc.

    An external supply supervisor is also required. There is an on-chip voltage monitor whose primary function is to allow the I/O and core supplies to be powered up/down in any sequence. The monitoring threshold are deliberately grossly outside of the recommended operating range to allow an external supervisor to affect a power-on-reset.

    TPS65381A PMIC is indeed designed to work with Hercules MCUs, and meets the requirements of both a supply supervisor and a CPU watchdog.

    Hope this helps.

  • indeed it does.  Thank you

  • Hello

    I always have a question,when I use tps65381. How to judge the 65381 startup is successful?

    Do I still need to monitor its operation in the program.use ENDRV?

    if two things have problem,There are safety risks

  • The application can also exercise the several BIST modes supported by the TPS65381. Safety analysis is usually done for a single-point failure. Multi-point failures can be detected by running self-tests on the logic blocks periodically or on start-u, depending on the “up time” of the application.