SLAU319AF July 2010 – September 2022
Power for the bootloader hardware can be supplied from the RS-232 interface. RS-232 signals DTR (pin 7 of the serial connector) and RTS (pin 4 of the serial connector) normally deliver a positive voltage to load capacitor C1 and power to the low-dropout voltage regulator IC1 (TI TPS76030 or LP2980-3.0, or equivalent 3-V low-dropout regulator).
Using a fairly big capacitor, it is possible to draw a short-duration current that is higher than the driving serial port can supply. This feature is required to program the flash memory, for example.
It is also possible to connect an external supply voltage to the hardware on pin 8 of the BSL target connector (J1). Diodes are used to prevent reverse-polarity flow.