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TPS3306-Q1: Watchdog disable while debugging/reprogramming

Roland Takacs
Prodigy 30 points
Part Number: TPS3306-Q1
Other Parts Discussed in Thread: TPS3306, SN74LVC1G125-Q1

Hello,

Our project uses the TMS5703137DZWTQQ1 microcontroller with a supply supervisor/watchdog IC TPS3306-25QDRG4Q1. The nRESET output of the TPS3306 is connected to the TMS570's nPORRST line with a 4.7k pull-up.
We are facing problems when debugging or re-programming the code in the microcontroller as the watchdog is asserting the nRESET line while doing so.

We are considering using a buffer with tri-state output (e.g. SN74LVC1G125-Q1) to buffer the WDI line between the micro and the watchdog. The datasheet states that the watchdog would re-trigger itself if the pin is left floating. Would this solution work even after the watchdog received previous pulses on the WDI without causing a micro reset?

Is there maybe other recommended way to resolve this issue?

  • 0
    TI__Genius 9375 points

    Hi Roland,

    I'm a little confused by the desired output you want. If it's startup behavior you want mitigated, you can keep the line high-impedance to allow the device to generate its own WDI during startup, and then deliver an input when you are done.

    Thanks,
    Abhinav.

  • 0 in reply to Abhinav.Sharma
    Prodigy 30 points

    Hi Abhinav,

    Thank you for the quick reply.

    The startup behaviour is not a problem. The system runs fine in normal operation. When debugging however, if the program is stopped at a breakpoint the watchdog will not get serviced anymore and that is what resetting the micro, losing debug connection in the process. As I mentioned we are proposing to use a 3-state buffer on the WDI line and the OE would be driven by the nTRST signal coming from the debugger. This would basically leave floating the WDI pin when programming/debugging is in progress. I already have the parts and hopefully can try this out soon to see if it works.

    Best regards,

    Roland

  • 0 in reply to Roland Takacs
    TI__Genius 9375 points

    Roland,

    This would be a functional way to do this. You need some way to allow WDI to stay floating in the startup phase to allow the device to generate its own.

    Thanks,
    Abhinav.