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what should we do for pins that must be not connected ?

Former Member

I am creating a component in the EAGLE library with only 3 pins and two others for the good fix, and after that I connect the pins, the two mounting pins I do not know what to do with, have you have any ideas?

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  • Hi,

     

    for 2 fix pin, create 2 pin connected to ground and asociate it with the 2 pad.

  • in reply to Former Member

    Hello,

     

    "Electrically" speaking, it's best to connect them to GND (floating metallic part are not good (in particular for radio/audio applications), and if the end-user can touch this metallic part, make sure to choose a signal that is safe for him, that why GND is a good choice).

    But I prefer to select a 'NC' direction for the pin, so I can choose to connect to an other signal in schematic. Useful when in one design you have different GNDs

    And usually, if theses two pads are electrically connected (by the part it self), then I create only 1 pin on the device, and I associate the two pads to this one pin. So I can not connect these 2 pads to 2 different signals (ie a short-circuit).

     

    "Mechanically" speaking, if this part must support some mechanical effort (if it's a connector, a switch etc...) these pad plays the fixing role. So connecting to a big plane is a good thing, specially if there are SMD type.

     

     

    Guillaume.

  • in reply to kikoun

    On 05/06/14 17:26, Guillaume barrey wrote:

    "Electrically" speaking, it's best to connect them to GND

     

    Surely, if they are "pins that MUST NOT BE CONNECTED", like the subject

    says, then you cannot connect them to ground because you'd violate the

    "must not be connected" part!

     

    If you mean "pins that have no internal connection" then what you said

    is all fair enough, but it's very important to make the clear

    distinction between these two common manufacturer statements. "No

    connection" and "do not connect" are not the same thing at all.

     

    Cheers,

    Rob

     

     

  • in reply to autodeskguest

    Hi,

     


    Rob is right, Do not connect  to any signal a pin that is mention as 'DO NOT CONNECT' in part datasheet.

     

    In fact the best way to do is to ALWAYS read carefully the datasheet, and if some doubt still subsist, always refer to the part manufacturer. Last year I contact Texas instruments because they didn't mention anything about the underneath thermal pad of a RS232 driver. at the time I supposed that it was a GND pad, but I prefer to ask them. They quickly answer to the question, (an add the missing information in their datasheet). It was a GND, Ok , but now I'm sure of it !

     

    Guillaume.