Question
Can I connect the AD711 pin number 8 ( which is NC) to ground
Answer
The AD711 was designed back East in MA, and I am in CA, so it will take me
some time to track down the correct bonding diagram.
Some general comments on "NC". _MOST_ of the time, semiconductor
manufacturers use NC to mean "no connection inside the package". But be
careful, some of them, on some parts, use NC, rather than DNC, meaning "do not
connect, there is something inside connected to this pin". Especially on
references, you may have three NC pins which are zener-zap pins, and there are
bond wires on these pins. For the super precision references, there is a small
shift in output voltage due to package stress during assembly, so we zener-zap
trim after assembly.
The safest course of action is to never connect anything to an NC pin.
However, with smaller and smaller packages, a customer may want to route a pc
board trace under the package, so they go through the NC pad. A really good
engineer will always ask the manufacturer before doing this, so I congratulate
your customer for being such a good engineer.