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MSPM0L1105: Question on MSPM0 lower power optimization guide

Shengyue Zhong
Intellectual 1300 points
Part Number: MSPM0L1105


Tool/software:

HI Team,

One question on MSPM0G3507 Low Power Test and Guidance, there is a suggestion on UART setting, user need to keep RX pulled up to avoid device get out of low power mode. However, when customer set MSPM0 into low power mode, the hardware pull-up power source would drop to GND, then RX turned to be 0V, which could not satisfy this condition, but the UART was not enabled as description above.

The customer wants to figure out is the phenomenon normal? This suggestion is hardware related, or software pull-up could be enough? How about the risk if RX could not keep pulled up in low power mode? Thanks.

  • 0
    TI__Mastermind 29105 points

    Hey Shengyue,

    Is the device the customer is working with G3507 or L1105?  

    As for the UART, are they disabling the UART when they go to low power mode?  

    From the description, my understanding is that having the UART RX low will look like a start bit and transactions causing the UART module to wake.  If the UART is being disabled, then this obviously won't happen. Based on your description of the customer's setup, I would suggest either using a different source for the pull--up or disable the UART when the pull-up power is removed and re-enabled when it's back.   (maybe using another GPIO to detect? )

    Thanks,

    JD 

  • 0 in reply to JD Crutchfield
    TI__Intellectual 1300 points

    Understood, thank you JD. Another puzzle is if UART has been waked, what will it be like, will any pin be pulled up? 

  • 0 in reply to Shengyue Zhong
    TI__Mastermind 29105 points

    I don't think any pin will be pulled up, you just might see a jump in current from the MSPM0 as the UART may request a fast clock which powers up more of the chip and/or the UART might fire an interrupt and wake the MCU saying it received all zeroes, ect.  

    Thanks,

    JD