Help with IC pinout

The stripe on the IC (left side in the picture) denotes the end of the first and last pins (1 and 14) . Pin one is lower left.

Hi Larry, yes sometimes manufacturers do not bother anymore with a notch or a dot. But what they do (instead) is on one side of the IC (the sides along the pins) they tend to taper one side of it and that would be (your key!) the side where you start counting the pins position the IC with the tapered side to your right. See picture below. They do however mention and show it on the DataSheet “Usually” but some manufacturers do not !

@ovi4 Only problem I am not seeing a tapered side.

I have to go back to the lab and double check, but not seeing it in my pictures.

Look at page 16 of the data-sheet issued February 1998 – Revised August 2003 it is actually pictured there:

@ovi4 You are so right, but I have to turn on end under the scope to see it.
I am getting so blind…LOL

@larry_n7luf Oh, rest assured Larry (you’re far from being blind) I myself have trouble finding it on some IC’s since sometimes looks dull (so no sharply cut edges) and because the package is the SMD style (SO, SOIC 14) that makes it more difficult to spot especially not knowing what to look for but…nevertheless it is (or should) be there.

@ovi4 I would love to show the board here, but should not show here it here, as I got to clean all the flux off the board now before the next step on the project.
For some reason my hands are very shaky but got the IC soldered in.

@larry_n7luf Just take it easy, one step at the time and always double, triple, quadruple check under the microscope for either not soldered pins or pin bridges. Of-course the best view is after cleaning the flux.

@ovi4 I didn’t know that trick. My guess was the line on the left side. Then again, I have not gotten into ICs yet as I am still waiting for circuit board stuff.

@radtekman well, it could ”in theory if there is no tapered corner (present) on the IC it could also be the line as well but…I don’t have that IC at hand to verify the theory. On the other hand I did came across many times to ICs (in devices that I had to repair) that had the writing removed or blurred so badly that even under the microscope you couldn’t distinguish anything clear info…forget about the dots or notches. So what do you do then? Well… there are some options:

1.you either have the schematic and try to reverse engineer the components around the IC and obviously in conjunction with it to work out the index.

2. if you can still workout the writing direction (even though you cannot clearly see what that is) then pin one is bellow the writing bottom left as you read and as the user “NQ8J” has mentioned in a post above.

3. look for the tapered edge (as mentioned previously) in hope is there.

Now going back to the above mentioned IC discussion about the that line. On the data sheet version I’ve looked at {February 1998 – Revised August 2003} there is no mention regarding the presence of that line as being the index pin (at least from what I’ve read so far) Only the tapered line is clearly shown as being the index.

Now, despite the evidence on the Datasheet, considering that Larry is saying that he couldn’t spot a tapered edge on his chip (at least not yet) the manufacturer (TI) might have “possibly” dropped the tapered line idea in favor for that line in later revisions /production of the above IC. it could well be the case (Who knows?) but, I’ve not seen any evidence of that (so far).

There are people on various forums that mention the line as a possible index. Perhaps is worth reading datasheet’s of other similarly packaged ICs to see.

Now, in an effort to further clarify the matter, I’ve discovered a very nice PDF document issued by the manufacturer NTE Electronics INC that refers to the indexing variants here: https://www.nteinc.com/faqs/IC_Pin1_Chart.pdf

Posted by: @larry_n7luf

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@ovi4 You are so right, but I have to turn on end under the scope to see it.
I am getting so blind…LOL

Yes he mentioned it right here. Collectively, there are a bunch of possibilities they could be implementing. All valid ways of identification.

@ovi4 That’s a great Identifier aid, lucky you came across it; and thanks for sharing it.

@brian-wood you welcome Brian