ST Microelectronics 393

Marked "393" and "(ST)GZ439" or "6Z439" under conformal coat.

Siemens DC/DC PSU section, near a UC3843B current-mode PWM controller, HF transformer, etc.

Checked the ST TS393ID datasheet, that is a micropower dual CMOS voltage comparator. Micropower doesn't make much sense in this application, and if it were that it should be marked "S393I". Checked TI's LM393D, nothing they make is marked with only "393" either.

But the other side of the two caps below it do connect to pin 4, so this seems fitting for a 393. Is this a custom marking, custom device, or?


1 Answer 1


How about the ST LM393?


There are ordering codes that are in a SOIC package and just marked "393". The second row could be manufacturing info.

Ordering Codes - page 18

  • \$\begingroup\$ Gosh, this appears to be a limitation of Octopart; it does not show ST's variant of the LM393DT, even though Digikey carries them. \$\endgroup\$
    – rdtsc
    Dec 16, 2021 at 18:47
  • 1
    \$\begingroup\$ @rdtsc, It's there if you search for LM393DT. I think your filters eliminated it from your search results because the package is listed as "SO" instead of "SOIC". \$\endgroup\$
    – The Photon
    Dec 16, 2021 at 18:55

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