I need to identify this part with the top marking M1K and seemingly no manufacturers mark, unless it's the underline. It appears to be an SOT23-5 and I've found some things about its pins based on measurements with my oscilliscope and seeing where it is in the circuit. enter image description here

As shown in the picture, the bottom left pin seems to have a pull-down resistor on it, and is always connected to the processor, due to that I'm pretty sure this is the output. The center left is ground and the bottom right may be the voltage supply. The top two seem to be the inputs. Both are not always used but when one is used, it's connected to the output of something else or the processor. My current thought is that it's some kind of voltage detector or switch but I haven't been able to find anything matching that. I have found parts with the same top mark but their pins never line up. Any nudge in the right direction is appreciated!

  • \$\begingroup\$ alltransistors.com gives a couple of possibilities. \$\endgroup\$ Jul 7, 2021 at 17:11
  • \$\begingroup\$ @AndrewMorton I checked out what it lists and none of the options line up with the pins I have, as in the GND and NC pins they list don't fit. Thank you for the help though. \$\endgroup\$
    – Jungush
    Jul 7, 2021 at 17:55
  • \$\begingroup\$ Oh well, it was something to check. Perhaps you could give more information on the circuit, such as what device it comes from and maybe a photo of more of the PCB. \$\endgroup\$ Jul 7, 2021 at 18:54

1 Answer 1


I actually found this part. After some searching, it appears to be this power switch. Found it on Mouser using characteristics I saw and searching switches.


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