[gta02-core] More symbols - FA2012, RT9711 and DTC123

Werner Almesberger werner at openmoko.org
Fri Jun 12 22:32:53 CEST 2009

Rene Harder wrote:
> Well I don't think they flipped the chip, they use this style for
> similar packages as well, right pin 1 to left  pin 2.

Ah, right. Even more confusing ...

> The questio is which style do we go for?

Almost everyone uses counter-clockwise numbering, with 1 at the
bottom left. Sometimes, they rotate the chip but stay clockwise.
Rohm's DTC123 is the only one I remember that uses a clockwise
numbering for a common package, though there might be some I've
successfully banished from my memory ;-)

> I see a lot of trouble here, we absolutely need to keep consistency.

Yes, agreed. Inconsistent pin numbering is dangerous. 

I'd say that we should try to keep the number of footprints low
and particularly avoid stray inconsistencies. So I'd go for a
clockwise numbering for this one as well. We can just pretend
it's not from Rohm, and nobody will even think there might be a
difference ;-)

Another issue is the package naming. According to Digi-Key:

Vendor	Package		Pin width (1,2)	Pin width (3)	Length, pin ends
Diodes	SOT-523		0.15-0.3	0.15-0.3	1.45-1.75
NXP	SOT-416, SC-75	0.15-0.3	0.15-0.3	1.45-1.75
ON Semi	SOT-416, SC-75	0.15-0.3	0.15-0.3	1.4-1.7
Rohm	EMT3		0.2		0.3		1.6

ON Semicondictor are nice enough to also include a footprint in the
data sheet:

All of them are well within the tolerances of each other, so
this is really a single footprint. I like the SOT-523 name,
because it tells me what this looks like (size class 5, the 2
is probably the number of sides, 3 pins in total), But SOT-416
or SC-75 seem to be "more standard" (?)

There are even crazier names in the field, such as Panasonic's
SSMini3, which is again a compatible footprint.

- Werner

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