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I've curious if there's an industry standard method used to determine the IC on a board. Specifically, I've been wondering as I have an IC that I want to replace. It seems to have failed, but there's not manufacturer mark. Is there a database somewhere where you can enter the code and get possible hits? In my case, my bad IC is a "DOT 201 139".

bad IC

The 201 is the manufacturer identifier, but no manufacturer has a "DOT" to my knowledge. Also, the SOIC-8 is really tall. This is enough information if there was central database to probably narrow it down, but I've been unable to find anything through web searches. I'm sure this problem isn't unique to me, and there must be some way that the IC industry agrees on how to find replacements, no?

update The circuit drives the gates of IGBTs that then run a solenoid. There's two of these drivers where one turns on and one turns off so that the coil field is bidirectional. It's weird that it's an H-bridge where the "center" is GND, so it has V+ and V- and then common, which is GND in this case. The best guess on the schematic is follows (I left off the connection to the 222 resistors): enter image description here

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    \$\begingroup\$ It might be an opto coupler. Is the same device higher up working? If so then look at signals in and out. \$\endgroup\$
    – Andy aka
    Oct 5, 2018 at 14:24
  • \$\begingroup\$ What makes you think the manufacturer wants you to know what devices they use on their boards? \$\endgroup\$
    – Finbarr
    Oct 5, 2018 at 14:24
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    \$\begingroup\$ There is no formal process. The IC industry does not care about this issue very much. Posting a picture here often leads to an answer. Do you have some idea what that part does or at least, what the PCB is used for or used in? It might help people guess better. \$\endgroup\$
    – mkeith
    Oct 5, 2018 at 14:34
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    \$\begingroup\$ Combine the high package and some experience and I would be thinking maybe a 6N139 optocoupler (But maybe not, the wiring is slightly odd), but there is no real formal process for this. You look at the details of the package, look at what you know, and what you know of the device, and start searching. Once you have a hypothesis you test it (On 1 '139 for example, LED is pins 2,3, which looks possible, but the output is clearly unconventional for that part). \$\endgroup\$
    – Dan Mills
    Oct 5, 2018 at 19:06
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    \$\begingroup\$ If you want to ID the chip, you have left out or hidden most of the information that would be helpful, such as the purpose of the circuit, known signals, the back of the board, and other chip markings. \$\endgroup\$
    – CL.
    Oct 6, 2018 at 13:11

3 Answers 3

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There is no formal process, unfortunately. Manufacturers may use numbers, letters, punctuation, and arbitrary shapes as meaningful symbols in top marks, I've seen all of these. Some manufacturers include datecodes, manufacturing location, lead-free status, etc, in addition to the part number in their top marking.

There are a few websites that provide lists of top marks with manufacturer/part number, however these are invariably incomplete. Keeping such lists up-to-date would be a massive effort. However, they can be worth checking, as you may get lucky. They are especially useful with parts that use numeric markings, such as yours, since numbers are unlikely to provide useful web search results.

Speaking of web searches, that's another option. I have had reasonable success in the past using search strings that include "IC top mark" and the marking in question. It may help to include the package as well, although there are usually three or more different designations for a given package that the manufacturer may use, which makes that a bit more difficult. This method works best when the manufacturer includes the top mark in their datasheets in a way that search engines can index. Some manufacturers are better about this than others.

Some manufacturers do provide an option to look up a part by its top mark, so if you can narrow the part down to a few manufacturers, it may be worth seeing if they offer such a tool.

If you can narrow down the function of the part, you may be able to use distributors' catalogs to narrow the search based on functional information (for instance, knowing it must have a voltage rating of at least X) as well as package to some number of manufacturers and part numbers, and then it's a matter of sifting through the datasheets and seeing if any of them have the right top mark.

The final option, is to simply not worry about what the specific part is, and focus on finding a functional replacement. This depends on a sufficiently thorough understanding of the circuit in question, but may give you a lot more flexibility in sourcing a replacement. You may wind up needing to go this route anyway if it turns out the part is obsolete.

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A component datasheet often will have a description of the markers that they put on their IC for users to easily identify the variation of the product that they have, the batch number, manufacturing origin, etc.

Some smaller chips have marking on the underside too, so you can try to desolder it and check the bottom part for clues.

If you don't know what IC it is then you'll have to try your luck with the search engine.

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The dot is not a logo; it's a pin identifier.

201 could be the manufacturer number and 139 could be a date code or the part number could be 201139.

Generally if you can't figure out the part, look at the use of the part on the board and what's it's connected to. If you can find anything on the other ICs around it, you may find an application note with the part referenced.

I like this site for as close to a database that I know of anyway:

http://www.s-manuals.com/smd

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    \$\begingroup\$ The dimple on the package is the pin 1 mark, the engraved dot is something else. It may or may not be meaningful in terms of identifying the part; I've often seen dots used to indicate lead-free status. \$\endgroup\$
    – ajb
    Oct 5, 2018 at 14:39

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