3 pin device near the USB port could be a voltage regulator, probably a low-drop regulator from 5V (USB) to 3.3 V (internal voltage of the pen). A quick internet search suggests the manufacturer of the chip was Anachip, now acquired by Diodes. But I couldn't fin more information with my quick search.
Check input and output voltages. If they match my hunch, the chip is propbably o.k.