What does N.C. really mean?

[bassmeister]

Most pinouts on ICs include one or more pins named NC, which means No Connection. But, does that mean that I may ABSOLUTELY not connect anything to that pin, or does it mean that it has no internal connection?

I'm asking because I lost a column when I hooked up ROGs Double D today. I had to take a long way around for one connection.

[SirPoonga]

I believe it means normall closed.  Meaning it doesn't do anything.

Ona  switch there is NO, NC, and GND.  Normally Open, Normally Closed, Ground.  I assume NC means the same thing here.

[pjwhite]

Some ICs have pins that are not connected to anything internally.  These pins would be marked N.C. on the IC symbol.  Sometimes in a circuit, the designer decides not to connect anything to a pin (maybe the balance connections on a LM301, for example).  These pins are connected internally on the IC, but would be labelled N.C. on the schematic.
And then there are switch and relay pins, as SirPoonga pointed out, that are labelled with abbreviations for Normally Open or Normally Closed.

[Torchy]

In my experience, if an ic pin says NC, then that means "do not connect anything to this pin" ie you isolate it. On a couple of datasheets Ive seen recommendations that these pins are connected to ground. On other sheets I have seen reference to these pins being connected to the substrate of the die. I dont think you can assume that the pin is not connected internally in some way. I just make sure that the pin is isolated and leave alone.

[RDV]

North Carolina, home of the "King Of Country & Western Troubadours".

RDV

[Mark Hammer]

In the context of the Double D, I *think* it means not-connected or "no connection", though the others are quite right in suggesting that it can also mean "normally-closed" in other contexts....and North Carolina in others.

You'll see NC quite often beside pins in multi-device chips.  So, for instance, in a hex invertor chip like a 4049, 4069, etc., not all the invertor sections are necessarily used.  Often the inputs of the unused devices have to be tied either high or low to keep noise under control but the outputs go unused.  The same is true for chips where there may be lotsa pins for additional features that are not used or implemented in that design.  These are often found on PCBs with a nice little donut pad around the IC pins in question, but no traces leading anywhere.  The "NC" designatuion is kind of a convenience for the builder, just to let them know that the reason why they don't seem to have a connection shown for that pin is NOT because they missed something, but because the pin remains deliberately unused.  Think of it like "roll call" - all present OR accounted for.

[R.G.]

It is a common error to connect *anything* to a pin marked "N.C." While some parts may have nothing at all connected to that pin inside (making it what, a monode??) many have stuff that the maker simply doesn't want or remember to tell you about, and connecting some signal may have repercussions from none at all up to destruction of the chip.

The absolute worst thing that can happen to you is that it makes the chip work a little funny sometimes. Try to figure that one out when your circuit doesn't work right.

[ninoman123]

No comment  

[Albert Kreuzer]

No chord...
not certain...
no clue  :wink:

Albert

[Incubus]

I remember I made a power supply once and I used a huge 1000uF capacitor.

It wasn't huge in terms of it's value, it was huge physically.....can't remember how many volts.

Anyway, because it was so big, it had 3 leads instead of 2.

Two were for the normal positive and negative connections, and the third was marked "nc", which was "not connected".

It was just there to help stabilise the thing and keep it steady.

[zachary vex]

It is a common error to connect *anything* to a pin marked "N.C." While some parts may have nothing at all connected to that pin inside (making it what, a monode??) many have stuff that the maker simply doesn't want or remember to tell you about, and connecting some signal may have repercussions from none at all up to destruction of the chip.

The absolute worst thing that can happen to you is that it makes the chip work a little funny sometimes. Try to figure that one out when your circuit doesn't work right.

isn't an antenna a monode?  8^)

[Peter Snowberg]

I think with an antenna, it's an anode or cathode depending on the part of the carrier cycle with the earth being the other 'electrode'.

I want a pedal powered by a magnetic monopole.

[puretube]

I`d use a dipole: symmetrical - less noise/larger headroom...

[Peter Snowberg]

Sorry for the hijack.... :| but NC = No connection so think of it as a big rambling footnote.


Why stop at one dipole? There is always the Sterba Curtain!  :twisted:

[R.G.]

isn't an antenna a monode? 8^)

Technically, no, it isn't. Antennas can look either capacitive or inductive from the driving side, and the other "terminal" is the whole of free space. It's a two terminal device, but the other terminal is quite diffuse.