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one pad multiple pins

jswift

v7.4

 

Section 8.4 of the manual describes how to hook 1 pin to multiple pads.

 

How does one create a part that has the reverse - multiple pins connected to 1 pad?

 

eg Diodes Inc AZ23C3V3 shared anode 2-zener in an SOT-23-3 package.

 

I want the 2 diode symbols to be separate, so that in schematic you can lay them out individually as desired.  Just like you would do for a multi-op-amp IC.  But what happens when creating the device is that the 2 symbols placed on the grid have 4 pins total.  When adding the package, the SOT23 footprint is not allowed to be selected because it only has 3 pins!

  • 0 in reply to autodeskguest

    Yeah in the general case that makes perfect sense, so for example you'd never want to publish such a library part.  Two mitigating factors here are that the parts are labeled 'A' and 'B' on the schematic; and I hope this would be caught when you update the PCB layout.

     

    Is there a way to logically connect the two pads in the package/footprint to tell Eagle that the 2 anodes must be connected to the same net?  There doesn't seem to be any support for that kind of thing.  That still wouldn't be perfect because Eagle doesn't make it easy to understand what exactly you are changing when it prompts you about connecting a pin to a net, but at least one could argue that explicit warning was given in the schematic editor.

  • 0 in reply to jswift

    On 01/11/15 06:08, Jonathan Swift wrote:

    I now see that elsewhere in the manual (p. 254 english manual) it says

    this is not possible.

     

    I created a package that has 4 pads, the 4th pad completely overlapping

    the 3rd.  It works as far as the part and schematic is concerned.  Will

    this work in the PCB layout?  I think that overlapping pads *in the part

    design* are ignored as far as DRC goes.

     

     

    It's not a good idea.

     

    You may think that your schematic looks better with the diodes separate,

    because they perform different tasks and just "happen" to share a ground

    pin, but showing it that way gives a false impression. In particular,

    future edits may want to decouple one of them from ground, and by

    showing them distinct the engineer doing so may not realise there's a

    problem. This can get VERY expensive when you run off a batch of

    prototypes with your reference line shorted to ground!

     

     

  • 0

    I now see that elsewhere in the manual (p. 254 english manual) it says this is not possible.

     

    I created a package that has 4 pads, the 4th pad completely overlapping the 3rd.  It works as far as the part and schematic is concerned.  Will this work in the PCB layout?  I think that overlapping pads in the part design are ignored as far as DRC goes.