Logically i understand that 'No Pin' literally means that there is no physical pin but i would prefer to hear a conformation of this fact by those who has encountered such situation. The thing is should i make a hole in PCB for the pin marked as 'No Pin' or not? In my case it's pin# 5 for PXE30-12S3P3 http://us.tdk-lambda.com/ftp/Specs/pxe.pdf And does it has any drawbacks if i have a hole in PCB under the IC part with "No Pin"?
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3 Answers
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I don't believe you need to place a pad for pin #5. That pin is only populated on the device with the dual output. That being said, it can't hurt to place a pad regardless. You can find the recommended pad layout for this device on page #56 in the datasheet:
http://us.tdk-lambda.com/ftp/appnotes/pxe30-xxSxx_datasheet.pdf
answered Jan 22, 2016 at 13:39
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2\$\begingroup\$ +1 I think it's best to make the footprints for the entire family of devices at once, that way the next time when you need a dual output device the footprint is waiting. You could use one footprint or two, of course. \$\endgroup\$ Commented Jan 22, 2016 at 17:49
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In general, most companies will use an NC - for Non-connect. But in this case, it looks like it really seems they do mean No Pin. Looking at the data sheet, you see that there are two variants of the part, one that uses that pin 5 (Dual output) and one that doesn't (Single output). Having a "No Pin" option allows the board to be designed to minimize part mix-ups during manufacturing, this is important since these packages look very similar and could easily be mixed up. Not having a pin hole will prevent a dual output device from being loaded in that position.
Sometimes, you put in pins and remove them when a part mix up will be dangerous or damaging, but with the pinouts on this part, there probably would not be a big flame out.
Also, since it is a hybrid package, the reduction of one pin will save one millicent (yes that is a joke) which over a production run of millions of units will save manufacturing costs.
There is a little bit of an art to reading a datasheet, so it's not surprising this could be confusing.
Although from the table snipped from the datasheet, it's not at all clear why a single output device would have two outputs ... (see pins 6 & 7)
answered Jan 22, 2016 at 17:37
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2\$\begingroup\$ The "+ Output" and "- Output" probably should be "Output +" and "Output -" instead. The +/- Output is misleading--It is not a positive and a negative output, but is more like an Output + and - like the + and - terminals of a battery. It is only one output. What grinds my gears is that they change this convention for the dual output, in which they DO mean a negative output and a positive output. \$\endgroup\$ Commented Jan 22, 2016 at 19:13
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It's a through hole component that uses one of TDK-Lambda's 'standard' packages. What I imagine is happening, is that they have other configurations where the 'no pin' is utilized and that they should have stated 'no connect'.
For assembly and manufacturing, I would recommend creating the through hole pad for the footprint, holes are generally free. If make the hole and don't use it, no big deal. If you exclude the hole and the pin exists, you have to snip it off before installation...
