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SOT223 and pins

autodeskguest

Hi,

 

I know we can assign a pin to two or more pads. Sometimes this is

necessary, indeed.

 

For example a SOT223 has four pads and usually the middle is connected

to the exposed one.

 

In the schematic makes no sense to show two pins: let's think a mosfet

with two drains....

 

What do you do to make the schematic readable and the layout correct

(e.g. both pads connected) ?

 

Thanks

Marco / iw2nzm

 

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  • Marco Trapanese wrote:

    Hi,

     

    I know we can assign a pin to two or more pads. Sometimes this is

    necessary, indeed.

     

    For example a SOT223 has four pads and usually the middle is connected

    to the exposed one.

     

    In the schematic makes no sense to show two pins: let's think a mosfet

    with two drains....

     

    Well, that is exactly what I end up doing.  Although it seems ugly at first,

    it actually makes good sense.  For example, I have a MOSFET on a schematic

    in front of me right now.  It's in a 4-pin DIP package, and looking at my

    schematic I can see that the drain is connected to pins 1 and 2, because

    both of those pins are shown on the symbol.  If the schematic symbol only

    had one drain pin shown, then I wouldn't be able to see both those pin

    numbers, and I might have to pull out the datasheet to figure out what that

    unknown pin is for.

     

    What do you do to make the schematic readable and the layout correct

    (e.g. both pads connected) ?

     

    Clench your teeth, put the multiple pins in the symbol, and with time you'll

    get used to it....

     

    Thanks

    Marco / iw2nzm

     

    --

    Bert Menkveld

     

     

     

Reply

  • Marco Trapanese wrote:

    Hi,

     

    I know we can assign a pin to two or more pads. Sometimes this is

    necessary, indeed.

     

    For example a SOT223 has four pads and usually the middle is connected

    to the exposed one.

     

    In the schematic makes no sense to show two pins: let's think a mosfet

    with two drains....

     

    Well, that is exactly what I end up doing.  Although it seems ugly at first,

    it actually makes good sense.  For example, I have a MOSFET on a schematic

    in front of me right now.  It's in a 4-pin DIP package, and looking at my

    schematic I can see that the drain is connected to pins 1 and 2, because

    both of those pins are shown on the symbol.  If the schematic symbol only

    had one drain pin shown, then I wouldn't be able to see both those pin

    numbers, and I might have to pull out the datasheet to figure out what that

    unknown pin is for.

     

    What do you do to make the schematic readable and the layout correct

    (e.g. both pads connected) ?

     

    Clench your teeth, put the multiple pins in the symbol, and with time you'll

    get used to it....

     

    Thanks

    Marco / iw2nzm

     

    --

    Bert Menkveld

     

     

     

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