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MSP430F5529: 1M ohm pull-down for PUR without push button?

Nate Enos
Genius 9450 points
Part Number: MSP430F5529


Hi Team,

Is the 1M ohm pull-down resistor for the PUR still recommended if no push button is implemented for BSL? From section 4.4 here:  

"The weak pulldown resistor on PUR ensures that the PUR pin stays low if the pushbutton is not pressed. (It is weak enough to not disrupt D+ during USB operation.) This pulldown should never be eliminated, as doing so might result in unintended invocation of the BSL."

When it says "never should be eliminated" is that assuming a push button? 

figure 3 from:  makes it look like it may be option due to the dotted outlined box. 

Thanks,

Nate

  • 0
    TI__Guru**** 219857 points
    Hi Nate,

    Footnote 2 from Section 1.6/Table 1-3 of the Family Users Guide states as such:

    "The default USB BSL evaluates the state of the PUR pin after a BOR reset. If it is pulled high externally, then the BSL is invoked. Therefore, unless invoking the BSL, it is important to keep PUR pulled low after a BOR reset, even if BSL or USB is never used. A 1-MΩ resistor to ground is recommended."

    Always populate the PUR 1M ohm pull-down resistor.

    Regards,
    Ryan
  • 0 in reply to Ryan Brown1
    TI__Genius 9450 points
    Thanks Ryan, that was just what I was looking for!

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