What is this SOT-23 part?
In cleaning up my office, I found a strip of SOT-23 parts that got separated from their identifications. The only markings are "R12":
I suspect it is a voltage regulator or reference, but it could be anything. I looked at a few datasheets, but none of them mentioned this marking or anything close to it. What is this?
In general, how does one get the full part number from abbreviated markings like this? Datasheets tell you markings from the part number, but manufacturers don't seem to have lists that do the reverse. Other than getting lucky and finding the right datasheet, how do you find the manufacturer and part number in a case like this?
1 answer
The following users marked this post as Works for me:
| User | Comment | Date |
|---|---|---|
| Olin Lathrop | (no comment) | Feb 24, 2026 at 15:08 |
I suspect it might be TI/National part: LM385M3-2.5/NOPB which is a SOT23 2.5V ref IC. But you have to hook it up as per that datasheet with crocodile clips and a bench supply to know for sure - if it gives out a 2.5V at pin 1 then I would assume it is indeed the correct part.
In general, how does one get the full part number from abbreviated markings like this?
It is hard. It helps a lot if you know it is a certain kind of IC and not a diode, BJT etc etc. There are some sites you can use, but they are not super-reliable. Examples:
https://smd.yooneed.one/
https://www.s-manuals.com/smd
In this case I used the former, then looked for SOT23 with R12 marking by non-exotic manufacturers.
Finally when you suspect a part, you can use the Chinese part vendor LCSC as picture look-up. They have a thing where they take a photo of all parts for sale. The TI/National part doesn't look too promising there since they show a part with the old National logo (Various copycat versions of it look more or less exactly like your part though). But TI ought to be rebranding these in new production with no National logo. There's some pictures at RS Online of what recently manufactured parts ought to look like - no National logo but not the same font as your part either. And it has some fab/date code underneath it too.
And finally there's AI - Google's AI seems to have come to the same conclusion as I did. But like me it is just making a qualified guess.
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