New Contributor
New Contributorak6dn et al,
I'm also concerned that stray low-current HV ESD impulse noise can fry an unconnected non-pulled up or non-bus-hold input, assuming it has negligible ESD withstand capability. Concern that a fairly low current ESD/surge stray can furthermore induce catastrophic latch-up .
What is even more concerning is what to do with a Cyclone IV's unconnected dedicated clock input pins! As far as I know there is no option for enabling bus hold or weak pullup in their assignments.
Regular ContributorFor any unused input, enable the passive pullup. No reasonable designer would let a CMOS input float. Don't do it.
Enable passive pullup, or add an external pullup/pulldown, as appropriate, for any iinput that may ever possibly not be driven by an external source.
