5V tolerance and pull-ups

lanchon · ‎2008-03-28

Posted on March 28, 2008 at 22:33

lanchon · ‎2011-05-17

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 · ‎2011-05-17

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.