Can you connect NC pin of 3 pin diode?

[cupoftea]

Hi,
We wish to connect the "NC" pin of the MMBD4148, SOT23 diode to the cathode pin.
(It will be easier to achieve clearances on the PCB, if we can do this)
Will this be OK?

MMBD4148

https://assets.nexperia.com/documents/data-sheet/MMBD4148.pdf

 

[KlausST]

Hi,

NC means internally not connected. So in first place I don´t see a problem in connecting it. (But read below)

However, I don´t see how connecting an NC pin can improve clearance.

Now that you talk about clearance, I guess it has to do with some safety regulations.
If so, then you need to consider high voltage on this NC pin. And the datasheet does not guarantee any safety isolation distances.

So when we talk about any safety distances, then I don´t recomment to connect the NC pin to anything.

Klaus

 

[cupoftea]

Thanks, i need to route to the cathode pin...and at the moment, am having to swerve round the NC pin, which is bringing me close to a track of high voltage elewhere, so i want to just route right through the NC pin, and so then to avoid getting design rule errors in layout, i want to just connect the track to this pin, on its way through this pin to the cathode.

 

[betwixt]

I know it's probably the most common diode on Earth but also consider what might happen if you had to use a substitute and the NC pin on the replacement was internally connected. If you do route through it, make sure you document it to prevent problems in the future.

Brian.

 

[wwfeldman]

what does the data sheet say about connecting the NC pin?

 

[std_match]

I say that it is OK. The maximum reverse voltage of the diode is 75V, so the internal isolation of the NC pin must only handle 75V if it is connected to the cathode pin.It will also work if a dual diode is mounted, as long as the "used" diode has the same direction as the one in MMBD4148.