SOP-4(ish)

[PlainName]

Looking at some optocouplers:

https://www.lcsc.com/products/Optocouplers-Phototransistor-Output_351.html

Specifically wanting a common SMD format which can be populated by multiple sources if necessary. So, SOP-4 looks reasonable and there's the list of 21 SOP-4 optocouplers. But half of them seem to be 2.54mm pitch and the other half 1.27mm pitch. They can't both be SOP-4, so which is really SOP-4? And what should the other lot be called?

[DavidAlfa]

The first one is SOP-4 100mil, the 2nd one is just SOP-4.
Is it really that hard to google "Optocoupler packages" ? 
https://www.vishay.com/docs/49633/sg2098.pdf

[thm_w]

Better to always check and not assume anything, IMO.
SOIC has various widths, I would not assume if they said "SOIC" only that it meant wide or narrow. Even Vishay themselves just write "SOP4" in the datasheet title.

[PlainName]

Is it really that hard to google "Optocoupler packages" ?

Did that, hence the confusion of which is actually SOP-4 - the wide one seemed to be 'real' SOP-4 but you say it's the other one 

[PlainName]

Better to always check and not assume anything, IMO.

Well, of course I would check the final choice, but knowing what to search for in order to make a choice that can be checked is part of the problem. Waste of time searching for the one I don't want

[DavidAlfa]

Still this is one of these packages triggering all alarms before production, can't trust pictures or descriptions, check the ordering code in the datasheet to make sure that it's the good one!
Same as the ususal soic/wsoic screw-up!
If your layout allows it, it's best to combine both footprints so you can use any when the next epidemic comes!

[nctnico]

Is it really that hard to google "Optocoupler packages" ?

Did that, hence the confusion of which is actually SOP-4 - the wide one seemed to be 'real' SOP-4 but you say it's the other one 

Always check the datasheet. There are many manufacturers who use the same name for an entirely different packages. Like QFN for example. These exist in 0.4mm, 0.5mm and 0.65mm pitches. And different case sizes as well despite having the same number of pins. I have stopped going by chip package names a long time ago.

[thm_w]

Better to always check and not assume anything, IMO.

Well, of course I would check the final choice, but knowing what to search for in order to make a choice that can be checked is part of the problem. Waste of time searching for the one I don't want

Sure, but that only works on sites which properly enter all of the data.
From your link LCSC has: SOP-4, SOP4-2.54mm, SOP4-2.8mm, etc. so you'll have to dig through to find what you want, assuming you want to check everything.

[PlainName]

If your layout allows it, it's best to combine both footprints so you can use any when the next epidemic comes!

Yes, I was thinking that might be a reasonable solution, though not so hot when space is at a premium.

[PlainName]

From your link LCSC has: SOP-4, SOP4-2.54mm, SOP4-2.8mm, etc.

Ding! Thank you - I've twigged now 

I thought that SOP-4 was a specific package but instead it seems to be a parent style for particular formats. That is, there isn't a simple SOP-4 package and instead it is always qualified. Except for manufacturer's data because they assume the one they use is the real one.