On "not connected" pins

Thread Starter

Andrew1234

Joined Feb 16, 2015
23
Hi
I am using an op amp (AD8139), and one of the pins on the SOIC-8 package is listed on the datasheet as NC. The datasheet clarifies that this pin is not connected to the IC internally to the package.

Should I literally not connect this pin to anything? Or is it safer for me to connect it to a fixed DC level, such as analog ground?

Regards
Andy
 

crutschow

Joined Mar 14, 2008
23,510
Generally it makes no difference whether or not the pin is connected externally, but it's probably good practice just to connect it to ground.
 

Hypatia's Protege

Joined Mar 1, 2015
3,197
Should I literally not connect this pin to anything? Or is it safer for me to connect it to a fixed DC level, such as analog ground?
Historically, the convention held that 'NC' (not connected) meant there was no connection to the die -- whereas 'reserved' meant 'leave it alone' (i.e. floating) ostensibly to assure 'backward compatibility' of future versions (albeit there were a good many 'undocumented connections' bearing that designation -- the Z8000 CPU series comes to mind) --- Unfortunately the convention failed to become standard and all bets are off -- that said, I concur with @crutschow - either ground it of leave it untied but under no circumstances 'count on' the untied pin to be merely floating...

Best regards
HP
 

dl324

Joined Mar 30, 2015
9,132
+1 for letting "no connects" float. No connect should mean that the pin isn't internally connected. Contrast that with a "do not connect"; which, obviously, should not be connected:rolleyes:
 

ErnieM

Joined Apr 24, 2011
8,006
Another vote for "no connection" being a direction rather that a description.

If they say no connect then don't connect it.

It could possibly have a function the Manu uses during their testing.
 

ian field

Joined Oct 27, 2012
6,539
Historically, the convention held that 'NC' (not connected) meant there was no connection to the die -- whereas 'reserved' meant 'leave it alone' (i.e. floating) ostensibly to assure 'backward compatibility' of future versions (albeit there were a good many 'undocumented connections' bearing that designation -- the Z8000 CPU series comes to mind) --- Unfortunately the convention failed to become standard and all bets are off -- that said, I concur with @crutschow - either ground it of leave it untied but under no circumstances 'count on' the untied pin to be merely floating...

Best regards
HP
Very occasionally in the past, a pin labelled NC has some production test function and NC ambiguously means "not connected", as in shouldn't be connected in any final application.

Its quite rare and the data sheets are usually clear about that if its the case. Nonetheless, its a possibility that shouldn't be overlooked.

If there's some particular danger of static buildup - maybe a 10M resistor to GND just to be on the safe side.
 

ian field

Joined Oct 27, 2012
6,539
I vote don't connect...:)
That's probably the best way to go, but the data sheet should be carefully searched for any directions on the treatment of pins with no apparent function.

With pins that go to an unused circuit block, there's usually a correct procedure. With logic it often as simple as tying high or low. With op amps, the simplest is tie the output back to inverting input, some op amps don't like saturated outputs, so it can be advisable to tie the non inverting input to some steady intermediate voltage level.
 
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