does anyone know what part this is?

I suspect it's some kind of tvs or reverse polarity protection diode. I can read what's written on it, but can't find anything on the internet with the info. Obviously it's a part from ST, but other than that I'm totally blank.


For those who can't read it, it says:


Help would be appreciated :)

  • 5
    \$\begingroup\$ To answer the question in the title, "Who knows what part this is?", Rohat Kılıç does! \$\endgroup\$
    – Transistor
    Oct 18, 2022 at 12:31
  • 1
    \$\begingroup\$ Also listed here: smd.yooneed.one/code4558.html \$\endgroup\$
    – rdtsc
    Oct 18, 2022 at 12:55
  • 1
    \$\begingroup\$ @Transistor I'm updating my answer accordingly :) \$\endgroup\$ Oct 18, 2022 at 14:21
  • 2
    \$\begingroup\$ @EeEmDee poll type questions are off topic here ... why do you need a list of people with certain knowledge? \$\endgroup\$
    – jsotola
    Oct 18, 2022 at 15:14
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    \$\begingroup\$ @EeEmDee, we're having a little fun at your expense, but there's a gentle hint to write more carefully. You can see Rohit's answer in the "edited" link or in the micro-text at the bottom of his answer. \$\endgroup\$
    – Transistor
    Oct 18, 2022 at 16:15

1 Answer 1


does anyone know what part this is?

I do.

It's SM6T39A, a unidirectional TVS from ST.


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