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F29H850DM: F29 behavior when VDD drop below 1.19V

Hang Yang
Expert 3286 points

Part Number: F29H850DM
Other Parts Discussed in Thread: TPS653860-Q1, TPS650366-Q1, F29H85X-SOM-EVM, LAUNCHXL-F29H85X

Hi team,

The F29 requires 1.19V minimum for VDD rail, however, this devices does not have a VDD BOR. Customer need to select a external monitor IC to monitor VDD. The range of VDD is very small, If the external BOR is set to be 1.19V, it's likely that the external BOR triggered by noise. Is there any idea how to select the BOR chip?

In the meantime, If customer selects a thresold below 1.19V, in some cases VDD may drop below 1.19V, in this case, what's the behaviour of the CPU? Does it lower the frequency automatically like ST devices did?

Regards,

Hang

  • 0
    TI__Mastermind 40140 points


    Hi Hang,

    We have added a section for Power Management options in the F29H850 datasheet below:

    • Recommended TPS653860-Q1 and TPS650366-Q1 Power Management ICs (PMIC) 
      • Companion PMICs specially designed to meet device power supply requirements 
      • Flexible mapping and factory programmed configurations to support different use cases
      • Functional safety compliant PMICs to support external voltage monitoring and watchdog timer MCU safety requirements

    "Related Products" 

    • TPS653860-Q1 - Functional safety-compliant multi-rail power supply for safety MCUs with Hardware integrity level up to ASIL-D. Refer to F29H85X-SOM-EVM for schematic reference.
    • TPS650366-Q1 - Functional safety-compliant multi-rail power supply for safety MCUs with Hardware integrity level up to ASIL-B. Refer to LAUNCHXL-F29H85X for schematic reference.

    Above will be added in the next publication release.  These options were added to address the need for voltage monitoring for both power rails on the F29H850.

    For the second question, lower VDD than specified min value may affect the execution of bootrom.  During bootrom execution, internal power rail monitors are gating the sequence of bootrom code execution and if the rails go below the thresholds then code may be force device reset.  Note that the internal power rail monitor thresholds are coarse and not intended for precision voltage monitoring, hence the need for an external monitor.  The F29H85x bootrom would not support derating the operating frequency for lower VDD core due to the internal voltage monitoring dependency.

    Regards,

    Joseph