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TPS65381 external reset

Hi,

will be possible to trigger a reset cycle from the RSTEXT pin? I need to trigger a MCU reset (connected to the TPS65381) from a secondary standby MCU. This is for a Dual Modular Redundancy architecture.

Thanks,

Jarno

  • Jarno,

    RSTEXT pin is used to set the Reset delay extension time. If the pin is connected to 0 Ohms the delay time 1.4ms and if the pin is connected to 22k ohms, the delay time is 4.5ms.

    If you need to reset the MCU, you will need to externally trigger NRES pin.

    Regards,

    Jay

  • Hi Jarno,

    There are a few ways I can think of that you could force TPS65381 to go through the RESET state and pull NRES low to reset the main MCU. First would be to directly pull NRES low with the secondary MCU, this will reset the main MCU, and if DIS_NRES_MON bit is used in TPS65381 the mis-match will be detected and SAFE state will occur in the TPS65381. Using the SAFE_LOCK_THR and NO_SAFE_TO bits you can configure the time the TPS will stay in SAFE state before it will go through RESET state (see figure 5-16). IF you are not using a dual core lock step MCU which would use the MCU ESM of the TPS to monitor faults it could be re-purposed as an input from the secondary MCU. The main MCU would use the watchdog in Q&A mode, the secondary MCU would then use the MCU ESM and issue a "fault" to the TPS when it wants the main MCU to reset. The TPS would again go to SAFE state, then with the configuration listed earlier the device would go through RESET state. Another way would have the secondary MCU interfere with the main MCU's ability to "feed" the watchdog where by the TPS would go to RESET state.

    Scott