library errors

[jg_geadinc]

Part Number       Pinout is        Pinout should be

---------------------------------------------------

J201                  SGD               DSG

VN0300L            DGS               SGD

2N3904              CBE               EBC

PN2222A            CBE               EBC

MPSA13              CBE               EBC

PN2907              CBE               EBC

2N3906              CBE               EBC

[yyao]

Hi there,

Thank you for reporting this. It looks like J201 and J202 have incorrect pinouts. We will fix this as soon as we can.

However, the remainder of the  parts that you listed are correct, although at first glance, they may not appear to be. The pinouts specified in the Edit Footprint dialog are mapped using the to the Ultiboard pinout information prior to being imported through Ultiboard. It just so happens that the Ultiboard pinout for the TO-92 package is set up to reverse the pin order that you have listed. This may seem convoluted, but this is done to maintain compatibility with other CAD packages. To view the Ultiboard pinout information, you can do this:

1. Double click the transistor. This will bring up its properties page.
2. Click on the Value tab.
3. Click on Edit Footprint.
4. Click on Select From Database
5. You will now see a large list of components which are available to Ultiboard. The active footprint is selected. Scroll to the side and identify the column labeled Ultiboard Pinout. You will see that for the TO-92 footprint, the Ultiboard pinout is specified as 3;2;1;. This tells Multisim to reverse the CBE sequence prior to exporting to Ultiboard. After reversing the pinout, the pin order will become EBC which is correct.

Hope that helps.

[jg_geadinc]

This does more than 'appear' convoluted. When I edit the part in Multisim, it shows me the footprint and the pin numbering and how they are mapped. And it is wrong. As a designer who is going to send this information to a PCB designer it needs to be corrected. From what you are saying it sounds like if I make it look right in Multisim, it will be imported reversed when I send the netlist to the PCB designer? It just doesn't make sense to me to have the only information available to me (using Multisim) appear wrong.

[yyao]

I do agree that is is confusing to work with. You can copy the components to your user or corporate database and modify them to suit your needs. The footprint in Ultiboard that does not reverse the pin order is TO-92(92). If you do change the footprint, please remember to modify the footprint mappings as well.

[yyao]

Hi jg_fs,

Your feedback and insight to this problem is very important to us. The issue of footprint pin ordering in our database has been around for a long time and is a tricky one to reconcile. We try our best to make Multisim easy to use while providing compatibility with other layout tools. Part of this confusion arises from how Multisim handles pin ordering to maintain compatibility with other layout tools. We spend a significant amount of effort correcting, improving and adding new components and footprints. We do our best to insure that the end result is a board which can be manufactured and behave correctly. Although the pin order appear confusing, the end result should be correct. However, we strongly recommend all design engineers to recheck their Gerbers prior to manufacturing as you have done.

Another part of this issue arises from the fact that semiconductor vendors cannot agree on pinouts. For example, compare the following datasheets on the 2N3904:

• http://www.nxp.com/acrobat_download/datasheets/2N3904_4.pdf
• http://www.onsemi.com/pub_link/Collateral/2N3903-D.PDF
• http://www.fairchildsemi.com/ds/2N/2N3904.pdf

You will see that the pin numbering differs between vendors and some prefer not to number them at all! Either way, any pin ordering that we choose would be disagree with one vendor or another. To make matters worse, it seems that JEDEC only specifies mechanical dimensions but has no input about the pin numbering of transistor outlines and there is no clear industry standard.

Currently, we are thinking of methods of eliminating this multiple pin ordering confusion. One idea we have is to create vendor specific footprints, one footprint per vendor and eliminate the need for custom pin order remapping. This way, when you place a component, you are guaranteed that the footprint mapping table matches what you find in the datasheet. If you have suggestions or other ideas, we would love to hear about them and take them into consideration for our future work.

Thank you.