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I've just soldered a SOIC-16 am26c32 on to a breakout board.

The datasheet shows the orientation of the chip by means of a semi circle at one end (http://www.ti.com/lit/ds/symlink/am26c32.pdf). However, on the actual device, there is no such semi circle to be found - only the name of the chip.

Am I to assume that pin 1 is the bottom left, when the chip shows the writing the right way up?

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    \$\begingroup\$ you don't happen to have a photo of the IC in question? \$\endgroup\$
    – Marcus Müller
    Commented Jul 30, 2018 at 16:54

4 Answers 4

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Mechanical Drawing

As Olin said, and as you can see from the mechanical drawing, one side should have a bevel.

Also, in practice, TI prints/etches/lasers a pretty clear bar onto the left hand side (in above drawing), something like:

soic

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  • \$\begingroup\$ I can see the bar. is that where pin 1 is then? \$\endgroup\$
    – 19172281
    Commented Jul 30, 2018 at 17:05
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    \$\begingroup\$ if that bevel is on the same side, yes :) \$\endgroup\$
    – Marcus Müller
    Commented Jul 30, 2018 at 17:11
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Some SOIC type of packages don't have a dot or semi-circle. The first row is designated by a bevel,

enter image description here

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Look more closely in the Mechanical Data section of the datasheet. It shows that the edge is shaved off along the whole row of pins that includes pin 1:

enter image description here

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  • \$\begingroup\$ Most likely the bevel is molded into the package from the tooling rather than being shaved off which implies a post packaging machining operation. \$\endgroup\$
    – Michael Karas
    Commented Jul 30, 2018 at 18:41
  • \$\begingroup\$ @Mich: Yes, of course. I was describing the shape, not the process. \$\endgroup\$
    – Olin Lathrop
    Commented Jul 30, 2018 at 19:48
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    \$\begingroup\$ I know you were describing the shape. It's the use of the word "shaved" that expresses a process. You could use the word "beveled" in its place. \$\endgroup\$
    – Michael Karas
    Commented Jul 31, 2018 at 9:31
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In addition to the features already mentioned, you may also see a white dot on the chip by pin 1. It's more common on DIL packages, but I've seen it on SOIC too.

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  • \$\begingroup\$ Sure, but the problem with these TI chips in particular is that there's no such marker. Turns out that the big bar drawn across the top means the same thing, but I'm a tiny bit astonished that they'd invent a new convention like that and not talk about it. I've been trying to figure out a TI TL9002 dual op-amp, and in the datasheet it shows a dot, but there's a bar/bevel in reality! \$\endgroup\$
    – SusanW
    Commented Aug 4, 2019 at 16:03

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