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Newbee: howto make device with 2 GND pins

Former Member

Like SOT223 a device having 2 pins internally connected in the device.

Sot224 pin 2 and 4(cooling pad) are the same.

I supposed that connecting  one pin it is also connected to the other.

However, on the board a airwire still remains. This is also true for a

sot223 device from the library.

I tried the mailto:GND@1 etc. naming, but seems not to work.

What am I doing wrong?

 

 

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Parents

  • On Mon, 26 Apr 2010, Michael Sansom wrote to us saying :

    What is the significance (if any) of using the "@" symbol in the

    example  above.

     

    The @ symbol in a pin name introduces a hidden suffix, so that it allows

    all the pins to appear on the schematic as just "GND". It also means the

    net table treats them as just "GND", so they all get automatically

    connected to the GND net.

     

    BTW, what I do in this situation is have GND1, GND2, GND3, .... as pin

    names on the symbol and then connect them all independently to "GND" on

    the schematic.  Works well.

     

    Yes, that works, but it requires you to explicitly connect them all,

    shows a fake ordering of ground connections, and usually doesn't match

    the data sheet. It's very reasonable for the tab of a SOT223 FET, where

    you may actually want to distinguish between the tab and the middle pin

    because you only actually need to connect one of them, but for a 64 pin

    LQFP chip with 8 ground pins, you want them all to be the same to ensure

    they're all connected (like the data sheet says they must be).

    --

    Rob Pearce                       http://www.bdt-home.demon.co.uk

     

    The contents of this | Windows NT crashed.

    message are purely   | I am the Blue Screen of Death.

    my opinion. Don't    | No one hears your screams.

    believe a word.      |

     

Reply

  • On Mon, 26 Apr 2010, Michael Sansom wrote to us saying :

    What is the significance (if any) of using the "@" symbol in the

    example  above.

     

    The @ symbol in a pin name introduces a hidden suffix, so that it allows

    all the pins to appear on the schematic as just "GND". It also means the

    net table treats them as just "GND", so they all get automatically

    connected to the GND net.

     

    BTW, what I do in this situation is have GND1, GND2, GND3, .... as pin

    names on the symbol and then connect them all independently to "GND" on

    the schematic.  Works well.

     

    Yes, that works, but it requires you to explicitly connect them all,

    shows a fake ordering of ground connections, and usually doesn't match

    the data sheet. It's very reasonable for the tab of a SOT223 FET, where

    you may actually want to distinguish between the tab and the middle pin

    because you only actually need to connect one of them, but for a 64 pin

    LQFP chip with 8 ground pins, you want them all to be the same to ensure

    they're all connected (like the data sheet says they must be).

    --

    Rob Pearce                       http://www.bdt-home.demon.co.uk

     

    The contents of this | Windows NT crashed.

    message are purely   | I am the Blue Screen of Death.

    my opinion. Don't    | No one hears your screams.

    believe a word.      |

     

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