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lanchon
lanchon
Associate III
March 28, 2008
Question

5V tolerance and pull-ups

  • March 28, 2008
  • 2 replies
  • 600 views
Posted on March 28, 2008 at 22:33

5V tolerance and pull-ups

    This topic has been closed for replies.

    2 replies

    lanchon
    lanchonAuthor
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 12:26

    hi,

    say you have a 5V tolerant input that can be externally driven way up to 5V. then, is it safe to turn on the on-chip pull-up? no risk of current injection?

    thanks!

    lanchon
    lanchonAuthor
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 12:26

    from the datasheet (5.3.12):

    ''6. Pull-up and pull-down resistors are designed with a true resistance in series with a switchable PMOS/NMOS. This MOS/NMOS contribution to the series resistance is minimum (~10% order).''

    seems like there might be current injection to VDD over the 30K~50K resistor, up to 0.1mA per pin @ 2V VDD.

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