user28317: There is a chip on Arduino UNO board which I can not find anything about. It is labeled RSR 09TI. It is placed near other power related components (see the image), but what is its purpose on the board?


user4143: I believe that is the dual op-amp that is used for both monitoring VIN to enable/disable the USB power, and as a buffer for the LED on pin 13.
In the schematic it's U1, and is an LM358.

28317: <p>There is a chip on Arduino UNO board which I can not find anything about. It is labeled RSR 09TI. It is placed near other power related components (see the image), but what is its purpose on the board?</p>

<p><a href="https://i.stack.imgur.com/wb3n8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wb3n8.png" alt="RSR 09TI"></a></p>
 4143: <p>I believe that is the dual op-amp that is used for both monitoring VIN to enable/disable the USB power, and as a buffer for the LED on pin 13.</p>

<p>In <a href="https://www.arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf" rel="nofollow noreferrer">the schematic</a> it's U1, and is an <a href="http://www.ti.com/lit/ds/symlink/lm158-n.pdf" rel="nofollow noreferrer">LM358</a>.</p>
