The integrated 3.3-V power system incorporates an integrated 3.3-V LDO regulator that allows the entire MSP430 microcontroller to be powered from nominal 5-V LDOI when it is made available for the system. Alternatively, the power system can supply power only to other components within the system, or it can be unused altogether.
The Port U Pins (PU.0 and PU.1) function as general-purpose high-current I/O pins. These pins can only be configured together as either both inputs or both outputs. Port U is supplied by the LDOO rail. If the 3.3-V LDO is not being used in the system (disabled), the LDOO pin can be supplied externally.
The LDO-PWR module (LDO and PU Port) is available on only the MSP430F645x and MSP430F535x devices.