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OMAP-L138 NMI pin pull-up?

Jonathan Healy
Intellectual 410 points
Other Parts Discussed in Thread: OMAP-L138

The OMAP-L138 datasheet (SPRS586D) clearly states in table 2.5, section 2.8.1, that the NMI pin includes an internal pull-up resistor.

However, section 2.9 of the datasheet states that if unused, NMI "should be pulled-high externally through a 10k-ohm resistor to supply DVDD3318_B".

Why is the pull-up required, and if the internal pull-up is insufficient, would connecting the pin directly to the supply be acceptable? We are short of both tracking and component space!

Thanks, Jon.

 

  • 0
    TI__Guru* 84005 points

    Jon

    I would classify pins like reset. boot and NMI etc as critical pins and will not recommend relying on the internal pull ups/pds. Highly recommend putting an external pull up on NMI.

    Have not seen anyone directly connecting to supply.

    Regards

    Mukul

  • 0 in reply to Mukul Bhatnagar
    Intellectual 410 points

    I get your point with regards to critical nets but if the internal pull-up can't be relied on, why bother with it in the first place?

    It strikes me as somewhat poor if we can't rely on features of the IC because TI haven't bothered to fully characterise it?

    If it can't be relied upon then it should be in the errata?

     

    Jon

     

  • 0 in reply to Jonathan Healy
    TI__Guru* 84005 points

    Recommendation for pull up on NMI etc, is standard across most devices in TI, nothing device specific. Several customers have got burnt by not putting this in the past on other devices too. Glitches on NMI will also be a function of your board design and noise immunity etc. I recommend following the datasheet guidelines on this one.

    Regards

    Mukul