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[MSP430F5438] Clarification on PMM8 Errata

cyberstorm
Prodigy 140 points
Other Parts Discussed in Thread: MSP430F5438A

Hi guys,

I need a clarification about the errata PMM8 described in the document SLAZ046D (http://www.ti.com/litv/pdf/slaz046d).

The document states that "Due to an unpredictable value of the supply current in LPM4.5, the mode should not be used".

Does this mean that I have to avoid the usage of both LPM4 and LPM5 modes? Or is it simply a typo? The previous SLAZ046D only mentioned the LPM5 mode.

  • 0
    TI__Guru 69857 points

    "LPM4.5" is what previously was referred to as "LPM5". We renamed it to better accommodate other modes that have since been introduced (LPM3.5). Basically, now the ".5" suffix means that the Vcore regulator is OFF, and with that the memory is not retained.

    For a detailed overview, please check the "Operating Modes" section in the MSP430F5xx Family User's Guide (http://www.ti.com/lit/pdf/slau208). It's on page 32 in the current revision of the document (SLAU208E).

    Regards,
    Andreas

  • 0 in reply to Andreas Dannenberg
    Prodigy 140 points

    Thank you Andreas for the quick and clear answer.

    Considering the PMM8 Errata, what LPM  mode would you suggest for the lowest power consumption? I think I will use LPM4 with interrupts disabled.

    Actually I need to simulate the power-off for a device that doesn't have a supply switch. Ater this power-off, device can only be restarted by removing and reinserting the battery.

     

  • 0 in reply to cyberstorm
    TI__Guru 69857 points

    Yes LPM4 with interrupts disabled would be your best bet in that case. Also, it's important that no peripheral is active which could force on the clock despite LPM4. It would be good to clear all the xxxREQEN clock request bits in UCSCTL8.

    Also, our upcoming MSP430F5438A devices will have this bug fixed and LPM4.5 will be fully usable.

    Regards,
    Andreas

  • 0 in reply to Andreas Dannenberg
    Prodigy 140 points

    thank you Andreas, your help is much appreciated!

    cheers

    Marco

  • 0 in reply to cyberstorm
    Intellectual 400 points

    Are there any TI App Notes or reference designs addressing the use of  the msp430f5438A battery backup feature (LPM3.5 & 4.5)?

  • 0 in reply to 7ACDRIVER
    Guru 227245 points

    michael said:
    Are there any TI App Notes or reference designs addressing the use of  the msp430f5438A battery backup feature (LPM3.5 & 4.5)?


    Why are you using tons of TAGs for your question?
    And why are you asking your question in a thread related to the MPP8 erratum?
    Don't tag your questions (only tag answers, as nobody will search for questions) and start your own thread instead of reviving old ones with (mostly) unrelated questions.

    Anyway what do you need a reference design or appnote for? All information you need is in the description of the LPM. It is a really trivial thing. Almost as trivial as attaching a supply voltage to the MSP.
    Also, nowhere in users guide nor device datasheet, the term 'battery backup' is used, so what feature are you talking about?
    The LPM3.5 and 4.5 mean (and this is explained earlier in this thread) that the ram retention is switched off to further reduce current consumption of the device. If an interrupt occurs (a timer in case of LPM3.5 or a port interrupt in case of LPM4.5), then the device will wakeup normally, but since everything is lost (this includes stack pointer, status register, port configurations), the device should immediately do a reset (e.g. by setting the PMMSWBOR or PMMSWPOR bits in the PMM) and initialize as if it were a normal power-up.

    No need for an applicaiton note or a reference design. At least not for LPM3.5/4.5. If you want to have a battery backup in case of a supply power fail, this is a completely different thing, has nothing to do with LMPx.5 modes (or any LPM at all) and completely depends on your intended application. The only place where the users guide talks about a backup battery (sort of) is in the USB section, which does only apply to the 5529, where it is possible to power the device by USB if possible and by a battery if not. There should be an appnote available.
    Yet I doubt the software part will work on a normal 5438A, as it does not have an USB controller and therefore no register bits to check.
    And the hardware is trivial.

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