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MSPM0G1506: Detection mechanism of LFCLKFAIL in NMI events

ryota imi
Prodigy 20 points
Part Number: MSPM0G1506

Tool/software:

Hi expert,

When performing air discharge on a board using MSPM0G1506, the MCU froze.

LFCLKFAIL in the NMIRIS register was set to 1.

Could you tell us the reason why LFCLKFAIL occurs?
The clock source is a crystal oscillator.
  • 0
    TI__Genius 10490 points

    Hello Ryota,

    Below are my commons:

    • Firstly check whether your external crystal oscillator works normally: Check the frequency value of the crystal oscillator and check the capacitors value you used.

    • Secondly, try to use the internal LFOSC to generate LFCLK and check whether this issue will also occur.
    • Finally, try to change another chip to use and check whether this issue will also occur.

    And add one common, because I will go home tomorrow for Chinese New Year, please reply to me in this post after 5th Feb if you have any further questions, thanks!

    Best Regards and have a nice day!

    Janz Bai

  • 0 in reply to Janz Bai
    Prodigy 20 points

    Hi Janz-san,

    Thank you for replying to the comment.

    ＞    Firstly check whether your external crystal oscillator works normally: Check the frequency value of the crystal oscillator and check the capacitors value you used.
    ->-> Crystal oscillator value is 32.768kHz. Capacitor values are 15pF. The load capacitance is determined by the crystal manufacturer's crystal matching.

    ＞Secondly, try to use the internal LFOSC to generate LFCLK and check whether this issue will also occur.
    ->-> This issue does not occur when the LFOSC function is used. In our system, the RTC requires high accuracy, so we need to use an external oscillator.

    ＞Finally, try to change another chip to use and check whether this issue will also occur.
    ->->  The same issue occurs with another chip.

    What event does the MCU detect to cause LFCTRFAIL? Is it a frequency mismatch?
    Could it be a change in the DC level? Any other possibilities?

  • 0 in reply to ryota imi
    TI__Genius 10490 points

    Hello Ryota,

    I have returned back office from Chinese New Year Holiday. It seems that the root cause is still the crystal oscillator or the circuit design. You can find that in the datasheet, it said that there are parasitic bond and package cap on the LFXIN and LFXOUT pin. In the datasheet, the calculated value is 1 pF which sees the parasitic bond and package cap on the LFXIN and LFXOUT pin is 2pF per pin.  In fact, the cap on per pin may be 5 pF in some cases, so please try to reduce the cap value you used in the circuit (decreasing from 15pF). And try another one crystal oscillator to do tests too.

    Best Regards,

    Janz Bai