# Using VBUS instead of the USB port to power a MCU

I'm using an EK-TMC123GXL, for now powering it from the PC. I have found some problems with some pins (ADC, PWM) that doesn't arise if I power it up applying 3.3V to its VBUS pin instead of connecting it to my PC.

However, in its user manual (part 1.5) I have read that apparently the only way to power it up is through either of the two USB ports it has, specifically 4.75 to 5.25 V. As explained above, I have been using it by aplying 3.3V to the VBUS pin, can this damage the board? How can it work with only 3.3V if the minimum stated is 4.75?

## What I have investigated

I have seen the schematics and the VBUS pin is connected to a 3.3V regulator. The name of the regulator, according to the schematics, is TPS73633DRB, which I haven't found. I have found this one though TPS763, which matches the beginning of the reference in the schematics. Below in the datasheet, I have found that the model TPS76333 has an output of 3.3V, so I suspect this is the regultor my board is using. Don't understand very well the schematics reference. The thing is that this voltage regulator, according to the datasheet, admits a maximum input voltage of 10V (part 7, Absolute Maximum Ratings). Then, can I power up my board with a 9V battery safely?