USB connectivity without an external PHY
The MSP430F5509IZXH integrates a USB 2.0 full-speed device controller, so the BOM drops the external USB PHY and associated crystal for low-speed operation. This is the main differentiator versus MSP430F5xx siblings that lack USB — for any design where the MCU talks directly to a host PC or charger, this part saves a few dollars and a square centimetre of board area.
Peripherals and I/O
On-chip peripherals include a brown-out reset, power-on reset, DMA controller, PWM timer, and watchdog timer. The 12-channel 10-bit ADC handles analog sensor inputs without an external converter. The internal oscillator keeps the BOM lean for applications that don't require a precision timebase.