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MSP430F6635 VBAT power up sequence

Jeffs_Fairway
Intellectual 290 points

I'm a newb at the MSP430, currently reviewing a design for a customer who's driving the VBAT pin from a 1.8V regulator and the rest of the part from a 3.3V supply.  The 1.8V LDO is enabled via a port pin from the MSP430 and so there is no voltage on the VBAT pin for some time after the processor is initially powered up.  Since the data sheet says to tie the VBAT pin to DVCC if unused will delaying the application of power to the VBAT pin on startup cause any issues?  I couldn't find anything in the data sheet related to power sequencing of the DVCC, AVCC and VBAT pins.

Regards,

-Jeff

  • 0
    TI__Guru 56685 points

    Hello Jeff,

    In order to use the Backup Battery System properly and keep RTC_B data intact, VBAT needs to come up before DVCC and stay powered if DVCC is removed. The exact times when VBAT powers the backup-supplied subsystem vs DVCC is captured in section 3.2 Battery Backup Operation within the User Guide (link). For more application information on using the Backup Battery System in conjunction with RTC_B please see the following application note, link.  If the customer is not using this functionality, then VBAT should be connected as instructed in the Connection of Unused Pins section of the data sheet.

    Regards,

    JH

  • 0 in reply to Jace H
    Intellectual 290 points
    Thanks for that, Jace. I'll pass the info along.

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