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Autodesk EAGLE
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EAGLE User Chat (English) Package variant with unconnected pins
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Related

Package variant with unconnected pins

Former Member
Former Member over 10 years ago

I'm making a symbol for the QFN20 and SSOP24 variants of the SIlicon Laboratories Si473x famiy devices. Apart from the SSOP having more NC and earth pins (which I can connect as duplicates), there's an extra pin (DYBP) on the SSOP which isn't brought out on the QFN. If I add this pin to the device, I get errors using the QFN package because it isn't connected.

 

Is it possible to have a pin in a device which is not available in all package variants? How?

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  • Former Member
    Former Member over 10 years ago

    What part of this question is difficult to understand? I'm assuming it must be, because other questions get answered, but not mine.

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  • dukepro
    dukepro over 10 years ago in reply to Former Member

    On 04/09/2013 09:46 PM, Clifford Heath wrote:

    I'm making a symbol for the QFN20 and SSOP24 variants of the SIlicon

    Laboratories Si473x famiy devices. Apart from the SSOP having more NC

    and earth pins (which I can connect as duplicates), there's an extra pin

    (DYBP) on the SSOP which isn't brought out on the QFN. If I add this pin

    to the device, I get errors using the QFN package because it isn't

    connected.

     

    Is it possible to have a pin in a device which is not available in all

    package variants? How?

    ...

    What part of this question is difficult to understand? I'm assuming it

    must be, because other questions get answered, but not mine.

     

    It's not it's difficult to understand, but more likely that no one has a

    good answer to offer.

     

    Just off hand, I'd say that it's not possible to have a pin defined in

    the device's symbol, and not have it connected to any pad in the package.

     

    When you say "I get errors" isn't real clear.  Exactly what is the error

    message, and when do you get it?  I assume you're getting an error when

    you try to add the QFN package to the device, but the QFN package

    doesn't have enough pins.

     

    One suggestion I would make is to create a separate device with a new

    symbol that doesn't have the DYBP pin defined.  Then adding the QFN to

    the new device shouldn't be a problem.  Down side: you now have multiple

    Si473x devices.

     

    Alternatively, if the DYBP pin is not needed or should be left

    unconnected for proper operation of the IC, you can remove this pin from

    the symbol, then add the QFN.  Down side: The DYBP pin is inaccessible

    for all packages.

     

    I don't consider these as "good" answers, but merely work-around

    suggestions.

     

    HTH

        - Chuck

     

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  • Former Member
    Former Member over 10 years ago in reply to Former Member

    Thanks, that's what I figured. I had just hoped that there was a different answer image.

    The errors I was getting were a result of not connecting the pad to anything in the

    SSOP, so you get an error when you try to place the SSOP. I hadn't yet added DPYB

    to the symbol, but that would cause the same problem with the QFN.

     

    Eagle's connection tool needs the ability to say "unavailable" for any pin in the symbol.

     

    Would it be possible to place an "infinitely" tiny pin with no keep-out etc, and connect

    to that, or would that create other issues?

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  • dukepro
    dukepro over 10 years ago in reply to Former Member

    On 04/10/2013 06:08 PM, Clifford Heath wrote:

    Would it be possible to place an "infinitely" tiny pin with no keep-out

    etc, and connect

    to that, or would that create other issues?

     

    Sure, you could add an extra pad to the package for that purpose.

    Position it somewhere where you're sure there will be no connection.

    When you place the pad, be sure to turn off the stop mask and cream

    layer properties for the pad itself.  If I recall correctly, these are

    check boxes in the properties dialog.  Just copy the QFN.pac to

    something like QFNx and modify the latter.

     

    Enjoy,

        - Chuck

     

     

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