yup, this is that is the way to do it, so many people run into trouble by trying to follow the vendor data sheet numbering system. You end up with chaos that way. By standardizing the footprint and then creating your schematic symbol pin numbering to match the physical footprint you avoid having problems. If you do have a problem it will be with just that one component (schematic symbo) and by being sure to check new footprints manually (visually) by comparing pcb-schematic-vendor data sheet you will be sure that all following uses of that part will be correct as well. Yo should only have to double check new components using this method.

PH

From: Darcy Davis <[EMAIL PROTECTED]>
Reply-To: "Protel EDA Forum" <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: [PEDA] SOT-23 pinout
Date: Fri, 16 Jul 2004 08:31:41 -0600

I wasn't going to stick my neck out but...What works for us is to have a
common PCB footprint (We use the same as Mira and others) and then we create
a unique schematic part for each part# we use. The pins of the schematic
part are mapped to the generic pad numbering in the layout footprint. While
reviewing, I no longer bother to try figure out the mapping. I just pull up
the datasheet and the PCB layout and check if the physical connection goes
where I want it to.


On a side note...until I started this process, we had to do the "dead bug"
thing more than I care to admit. The worst part is that legacy [incorrect]
footprints still exist in older designs waiting to strike the next time we
rev a board.

Don't get me going on the lack of clear datasheet mechanical information!
Overconstrained parts, missing dimensions, lack of regard for controlling
units etc. all make me see fuzzy. Technical drawings aren't that hard are
they? ;-)

Darcy Davis
Design Engineer,
Dynastream Innovations, Inc.



-----Original Message-----
From: Ian Wilson [mailto:[EMAIL PROTECTED]
Sent: July 15, 2004 10:46 PM
To: Protel EDA Forum
Subject: Re: [PEDA] SOT-23 pinout


On 02:15 PM 16/07/2004, Dennis Saputelli said: ><..snip..> > >BTW remember the To92's that were ECB ? (or was it BCE ?) >just get out a bit of sleeving and your solder sucker and you >were all set >quite a bit harder to deal with in the case of SOTs though


I have seem prototypes with SOT-23 upside-down with the gull-wing legs bent to meet the board. It would have been done in a small production run except reverse pinned versions were available. Worse think about this was that another design done shortly after suffered the *same* problem - I couldn't believe the lack of care and attention to detail.

Ian



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