I'm trying to find the components of the PCB I have. I have a problem with a 5 pin (SOT23-5) component. Can someone help me with this?

There are version1, version2 and version3 of the PCB and marking codes are AA43, AA44 and AACB respectively.

There is a reset button and an error switch on the board. I measured the voltage values ​​when I pressed any of them (see schematic.)



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    \$\begingroup\$ Props for a readable schematic imaged with something better than a potato, and for nailing the important signal levels and such. Good job! \$\endgroup\$ Commented Mar 31, 2022 at 18:09
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    \$\begingroup\$ Once you've contributed a question to this site, it gets kept for the benefit of future readers, which is allowed by the Terms of Service you agree to before contributing. No destroying the question. \$\endgroup\$
    – Ben Voigt
    Commented Apr 1, 2022 at 15:05
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    \$\begingroup\$ I rolled back your editing. There is no reason you deleted the schematic and the photo. You also got lots of upvotes because of that. I fully agree with @BenVoigt. \$\endgroup\$ Commented Apr 4, 2022 at 11:25
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    \$\begingroup\$ If you deleted that schematic and that photo because you want to preserve some IP right, well, sorry: this is not a free design service. When you post something here you relinquish some rights about the things you post (see the license and terms of service). \$\endgroup\$ Commented Apr 4, 2022 at 11:27

2 Answers 2


The usual search from s-manuals (https://www.s-manuals.com/smd/aa) didn't bring useful results.

The part looks like a low voltage op amp judging from the schematic. The right-hand side sub-circuit looks like a low-pass filtered non-inverting amplifier which converts the load current of the top-right NMOS to voltage. And the output goes to MCU (probably to ADC) through another RC low-pass filter. The other sub-circuit to the left is a buffer which gets its input from MCU/1.24V through a RC filter+divider and generates a reference/bias voltage for the amplifier stage for accurate/sensitive current measurement.

So what you can do is to search single low-voltage op amps with SOT-23-5 package from Digikey, Mouser, etc. and check their markings.


This is roughly how that circuit can be re-drawn:


simulate this circuit – Schematic created using CircuitLab

And here is it re-drawn to be easier to follow:


simulate this circuit


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