2114 Static RAMs...

From: David V. Corbin <dvcorbin_at_optonline.net>
Date: Wed Sep 15 12:40:18 2004

>>>
>>> Thim makes me conclude that in order to correctly measure
>>> stand by current consumption on any CMOS circuit, you
>>> _must_ tie all unused inputs to either Vdd or Vss,
>>> whichever makes most sense.
>>>
>>> If the input of a CMOS inverter is left floating, there is
>>> a good chance it will stay somewhere in the middle between
>>> high and low and both transistors will be half open for
>>> current to flow all the way from Vdd to Vss. If the input
>>> is tied to Vdd or Vss, then at least one of the transistors
>>> will be shut off, and very little current will flow. This
>>> is all there is to CMOS low static current con- sumption.
>>>

The above is quite correct. Over current is merely one of the effects of
Leaving CMOS inputs floating. What gets real interesting are the
bi-directional pins which
Need to be terminated when they are inputs, but not HARD tied when they are
outputs.
This offten requires some "scaffolding" curcuitry to power up a board
"outside of its native habitat".
Received on Wed Sep 15 2004 - 12:40:18 BST