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I am trying to replace a voltage regulator - the chip has 3-pins (2 on one side, and 1 on the other) and is marked as 15P. It is also marked with NH (or HN) rotated 90 degrees along the short side. I believe it is 3.3 volt output and likely the max input is around 7 volts. Chip measures 1.4 x 2.9 mm.

 _________        
|   15P   |            
|_________|

I have a second board that is not broken so I have added two pictures:

enter image description here

enter image description here

The first picture (can see 15P on the chip) shows the top pin connected to the +ve of the battery and the lower two pins connected to a resistor on the other side of the board. The resistor is shown in the second picture.

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    \$\begingroup\$ Are you sure it's a voltage regulator? Do you have an overview photo of the part in question and the surrounding circuit. From the size it's a SOT23-3 package. Marking 15P could be e.g. this P-Ch MOSFET which also matches the 90 degree HN indicating November 2020 as a date code. \$\endgroup\$
    – Tom Carpenter
    Commented Jul 8, 2021 at 23:23

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The dimensions you have given indicate a SOT23-3 package.

In the question you state voltage regulator, but now that you have provided a picture, it's more likely that it's an P-Channel MOSFET being used for reverse polarity protection, which would have Drain as the input, Source as the output, and Gate to ground.

The part is most likely DMP1045UQ from Diodes Inc.:

Clipping from the datasheet showing part markings

The marking of this part would be 15P along the chip, with an additional two-character date code placed 90 degrees from the main marking code. As can be seen from the image, HN does correctly decode into a valid date code of "2020 November".

As a bonus, the part below in the picture, in the 5-pin SOT23-5 package marked SH1B is a switching regulator, the LMR62014 from Texas Instruments. This will be doing the voltage regulation from the battery.

Switching Regulator Pinout and Marking

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  • \$\begingroup\$ I believe you are right. 1. The date code matches the board build date. 2. The chip layout matches. 3. The D pin connects to the positive battery and G/S pins connect to resistor. \$\endgroup\$
    – rpg007
    Commented Jul 9, 2021 at 0:20
  • \$\begingroup\$ but it should be the source pin at the positive side. @rpg007 \$\endgroup\$
    – tobalt
    Commented Jul 9, 2021 at 1:02
  • \$\begingroup\$ I will add a picture just in case it helps others in the future see what this is. \$\endgroup\$
    – rpg007
    Commented Jul 9, 2021 at 4:15
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    \$\begingroup\$ @tobalt Not if it's being used for reverse polarity protection. \$\endgroup\$
    – Hearth
    Commented Jul 9, 2021 at 4:49
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    \$\begingroup\$ @rpg007 You could just run a wire from the source pin to the drain pin, that would effectively bypass it. Alternatively pretty much any PMOS with simular package and specs would do. Nexperia PMV27UPER would work fine, as would Vishay Si2333CDS. \$\endgroup\$
    – Tom Carpenter
    Commented Jul 11, 2021 at 8:11

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