I am planning on using a quad optocoupler IC named ISQ203XSM (http://www.farnell.com/datasheets/90948.pdf?_ga=1.159355187.80908598.1463646290) and am confused regarding the dimensions of the SMD pckage. The datasheet doesn't seem to mention if this is a generic package like an SOP or TSSOP and the dimensions seem incomplete. Is there something that I am missing here?

I also emailed the company that manufactures these to clarify the matter and I haven't received a reply from them.

Thank you in advance for any help!

enter image description here

  • \$\begingroup\$ Its a "Gull-Wing" package. Same shape & size as a DIP, but with the ends of the leads bent out to sit on the surface of the PCB instead of going through holes. \$\endgroup\$ – brhans Jan 24 '17 at 16:13
  • \$\begingroup\$ Also, what specifically are you missing from that dimensional drawing? \$\endgroup\$ – Marcus Müller Jan 24 '17 at 16:16
  • \$\begingroup\$ "Its a "Gull-Wing" package. Same shape & size as..." @brhans I was not familiar with a Gull-Wing package. I will look it up. Thank you for the clarification. May I ask how you figured this out from the datasheet? \$\endgroup\$ – Rhydo N Jan 24 '17 at 16:17
  • \$\begingroup\$ @markus I was missing the top view of the IC (and the pad dimensions). I wasn't aware that the dimensions of the DIP package were supposed to match the surface mount package. \$\endgroup\$ – Rhydo N Jan 24 '17 at 16:21
  • \$\begingroup\$ You can simply draw the pad locations on the layout. All the dimensions are given to you. I would not use a generic package type like DIP dimensions for this. Just create a new one with your layout tool. \$\endgroup\$ – 12Lappie Jan 24 '17 at 16:26

As brhans said, the SMD package is actually the same as the DIP package. It has the same dimensions and shape, the only difference being the way the leads are bent. This is why they don't show more than the lead dimensions and the distance between board and package on the specific SMD drawing.

This is very common for optocouplers. Since an optocoupler is, well, a LED coupled with a sensor, with some clearance between them, there isn't much room left in the package to shrink it, unlike regular chips, which contain more plastic than silicon.

If you're just worried about dimensioning the pads appropriately on your PCB, you can base your footprint on other, simlarily packaged products. Here is an example from Vishay (SFH6156, taken randomly). The pad layout seem similar (although there are more pads on your chosen optocoupler).

enter image description here

  • \$\begingroup\$ There is no problem putting the same optocoupler into a smaller package; the reason for a larger package is the larger clearance. \$\endgroup\$ – CL. Jan 24 '17 at 19:14
  • \$\begingroup\$ That was what I meant to say yes. Since there is some clearance between led and sensor, you can't shrink much without reducing this clearance (and that would then make a different optocoupler, with different specs). Maybe I wasn't clear(ance). \$\endgroup\$ – dim Jan 24 '17 at 19:45
  • \$\begingroup\$ Basically every optocoupler uses a 0.4 mm clearance between LED and detector (and most are vertical anyway); with "clearance", I meant the distance between the pins. \$\endgroup\$ – CL. Jan 24 '17 at 20:29
  • \$\begingroup\$ Oook, sorry I didn't got what you meant. Well, you're totally right. \$\endgroup\$ – dim Jan 24 '17 at 20:33

It's "surface mount DIP" - i.e. it's a DIP where the legs have been bent outwards rather than left straight.

That end section gives you the shape of the legs, and all the other 'plan' (top down) drawings are the same for both SM and TH versions.

It's very common on opto-isolators, and also 'dip-switches'.


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