Electrical Specifications UART on J12 (Pin 39/40) on TMDXICE3359

If you mean UART4 on pins 39 and 40 of J12, this comes out directly from the processor at 3.3V logical levels.

You're right, i mean the UART4.

In which document can i find this Information?

In the ICE schematics: http://processors.wiki.ti.com/index.php/AM335x_Industrial_Communications_Engine_Board_Design_Files

I found the UART4 on J12.

Buuut.. where can get the information that this is 3.3V?

Because VDD is 3.3V on pin 1&2?

For this you have to trace the nets back to the processor and see which processor pins they come from. Processor pins are powered from one of the VDDSHV[1:6] processor power supplies. This can be seen from the AM335X Datasheet Rev. G Table 4-1. Finally you have to see where the power supply comes from. In this case it's VAUX2 powering VDDSHV6, and VAUX2 is a 3.3V LDO in the PMIC (TPS65910A User Guide).

Thanks! This answered my question :)