trouble ID'ing a SMD device

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I hae a SMD device (SOT-23-3). I am trying to figure out what it is. It is very clearly labelled with "109". No other text at all. It is very clear and it does not appear to be letters "I" or an "O", just numerals: 109.

Does anyone have some suggestions as to what it is? The way it is in the circuit, it would NOT appear to be a simple transistor. I think it is an IC of some sort.

-Tony

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Tony, if you can give us some context with it's application. For example, microchip have a range of reset devices in that package. So you have gnd, vcc and a open collector reset output. So if your device was near a micro and had these connections, then we could guess it is a reset device.

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Three terminal could be a reset device, voltage reference, temperature sensor, serial number, voltage regulator or a bunch of other things.

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Each manufacturer has its own set of ID numbers for SOT-23 devices. You are kind of stuck unless more information is available.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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This is useful...
http://www.marsport.org.uk/smd/m...
but does not list 109...
So is this, but not so good
http://embedeo.org/smd_codes/
Neither finds '109'
Here is another one...
http://www.random-science-tools....

Could it be '10' with the 9 being a date code ?

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Seems to me if you don't know what an SMD is, you're often out of luck.

They used to print ID on only SOME of the IC's. You had to know what it was from what bin you put it in.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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Well, it is likely to be some sort of shunt amplifier. I believe it is being used to measure the current thru a 2mR resistor at something like 8-22A. But I am not sure how it is supposed to work. I am working on deciphering the circuit.

Os, I believe one of the 3 pins is to one side of the resistor, and another to the other side, and the 3rd is an output. beyond that I can't be sure because I have to decipher the codes on the SOT-23-3 devices that I think are transistors!

-Tony

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For a current limit circuit there is the sense resistor between E and B. C is used to shutdown the current by whatever means. From what you're describing, it is just a transistor.

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Possibly one of those current monitor ICs that Zetex (now Diodes) made.

http://www.diodes.com/datasheets...

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AH HA! That is it. How did you find it? Now that I know what is it, I went back to digikey and found another way to search. Since there are comparatively few SOT-23-3 "integrated circuits", I did a search for that package. Then under "integrated circuits" there are a limited number of possibilirties. Under "current management", it is at the top of the list! This only worked because the package greatly restricted the number of possibilities.

I wonder why the "109" didn't appear in the SMD listings that weere mentioned in the initial replies to my original post?

-Tony

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The above sources listed for marking IDs are limited. Another source is Linear Technology http://cds.linear.com/docs/Packa... . I wish the other manufacturers had thier act together this well. This has saved me countless hours of research.

Hope this helps.

Roger

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Quote:
AH HA! That is it. How did you find it?

I'm amazed myself that I found it ;) But I once used this little chip and as 109 is quite similar to 1009 I just took a look at the datasheet and it happens to be the part you're looking for.