[gta02-core] More symbols - FA2012, RT9711 and DTC123
rehar at saweb.de
Fri Jun 12 23:39:28 CEST 2009
Werner Almesberger wrote:
> 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 ;-)
Well, for the most IC packages (SOP, TSOP, QFN etc.) i agree but I've
seen so many different variations in the pin numbering of SOT packages i
really can't tell what is "the standard" for transistors.
> 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 ;-)
Why clockwise? I would go for counter-clockwise (pin 1 bottom, left),
thats what ON, NXP and Diode is using, so 3:1. ;-)
> 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:
Rohm includes all the transistor footprints in a separate document.
> 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" (?)
Rohm recommends a pad size of 0.6x0.7 (mm) for the EMT3 package compared
to ON 0.356 x 0.508 (mm) SOT416. Thats quite a difference although the
pitch and actual pin size is almost identical.
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