Need help identifying SMD diodes.

[Traceless]

Hi everyone,

I have 3 different types of small form factor SMD diodes here. Two similar ones labeled "RN BP" and "RN WU", SOD-123FL form factor. I think those may be TVS diodes. I found similar looking ones here. However while the photo looks similar to the ones I have (except for the gap in the bottom line below the letters), the datasheet linked in the online shop does not match. 1st Littlefuse diodes should have the "LF" logo, second there is no type code "RN" or "WU" but only "BP" in that datasheet. I assume that two of the letters probably encode production date/facility and the other two the actual type.

The 3rd diode is SOD-123 (non-FL), its marking is really hard to photograph but it is labeled "CH W7". In contrast to the other two one end is marked with a single line above the letters (in contrast to the triple lines below the letters on the other two).

[pcprogrammer]

More likely zener diodes.

W7 ==> https://www.s-manuals.com/smd/w7 ==> 4.3V
WU ==> https://www.s-manuals.com/smd/wu ==> 33V 
BP ==> https://www.s-manuals.com/smd/bp ==> 16V 

I searched on google for "smd markings w7", etc.

[Traceless]

Hi pcprogrammer,

I also looked at those sites already. Problem is that the ones I saw there have different package formats or different markings. E.g. following your WU link there are only two SOD-123 types listed (from Diodes Inc. and Panjit), but the ones I have here are SOD-123FL (i.e. contacts at the bottom). There is a BZT52H Diode in the correct package SOD123FL but the top-mark is different. The closest match I saw was the picture in the Bürklin shop I linked above.

My W7 one in the non-FL package could be a zener and might match the Panjit, not sure though because there are no details in the Panjit datasheets about the top mark. The Diodes Inc. W7 ones are different because according to the datasheet the type code must be rotated by 90° relative to the date code. Its barely visible on my picture but the letter orientation is the same on all three diodes so the leftmost diode has "CH" on top and then in a new line "W7". The only difference between the first diode and the the other two is that the first has a non-FL package and one line above the letters as opposed to the 3 lines below the letters on the other two.

[pcprogrammer]

Hi Traceless,

that is the problem with these damned smd markings. 

So many companies that use the same letter and digit combinations to mark their components.

I just received a bunch of zener diodes from Aliexpress and they have the W. marking like W2 for 3V, and based on that I assumed yours to be zeners too. But you are correct on the orientation of the text. On mine the W. is inline with the components pins.

With the RN being the same on the two components I wonder if it is a manufacturer code, and it might be Sanken Electric USA Inc. Actually a Japanese company.

[fzabkar]

Your Buerklin link has the same photo as Mouser.

BG = SMF13A, unidirectional 13V TVS diode:

https://eu.mouser.com/new/littelfuse/littelfuse-smf-tvs-diodes/
https://eu.mouser.com/images/marketingid/2023/img/170324045.png?v=070223.1033 (photo)
https://eu.mouser.com/datasheet/2/240/Littelfuse_TVS_Diode_SMF_Datasheet.pdf-1698977.pdf (datasheet)

The photo in the datasheet doesn't match the marking style, but Mouser is a trusted supplier. :-?

[Traceless]

@pcprogrammer: Thanks for the reference to Sanken Electric. I checked their website they do produce, rectifier, snubber, fast recovery shottky and TVS diodes. However their products seem to come all in larger packages and are mostly either throughhole (e.g. TO220F, TO252 etc.) or much larger SMD packages like SZ-10 or SJP.

@fzabkar: One of the markings on one of the two SOD-123FL diodes include a BP (not BG), which according to the datasheet could be a SMF16A. The problem is that the 2nd diode has exactly the same marking style but is labled "RN WU" there is neither an entry for "RN" nor for "WU" in the Littlefuse datasheet which together with the fact that the Littlefuse logo is absent on both diodes indicates that the diodes I have here are not from littlefuse (or they might be an older product style with different markings)?

The photo in the datasheet doesn't match the marking style, but Mouser is a trusted supplier. :-?

The photos in those online shops are often problematic (mouser is no exception) they don't photograph every product but sometimes just use placeholders or reuse identical photos for an entire product line. I was recently searching for a resettable SMD fuse with a specific top mark but if you search on mouser for PPTC you get a list of items where many have the same image (i.e. the same top mark) even though the fuses have completely different ratings. For instance there at least 4 listed items labeled "LF 185" one is 72V 0.5A, one is 60V 1.5A another one is 72V 0.35A and then there is even a 33V, 2.6A with the same marking. Another example are PPTC 63V POLYFUSE 0805 0.02A and PPTC 16V POLYFUSE 0805 0.20A both have vastly different ratings but a photo with the top mark "E". So the general rule for me is "Rely on the datasheet not the photo."

[pcprogrammer]

Have you tried to measure on them? With a power supply with adjustable voltage and current limiting you can try to find the tipping point. This will at least give you a hint about the working voltage.

To bad the Sanken did not pan out, but this was the only one that came up with RN. For example this one.

Do you have an idea about the circuit they are used in?