The 108-ball BGA (10x10 mm package) keeps the footprint compact, though the fine pitch means your PCB fab needs via-in-pad capability for the center balls.
Peripheral set: Ethernet, CAN, USB OTG, and more
This part packs connectivity that typically requires an external PHY or bridge: Ethernet MAC, CAN 2.0B, USB OTG, plus multiple UART, SPI, I²C, and SSI serial interfaces. The EBI/EMI bus lets you attach external memory or FPGA-style peripherals without a glue-logic CPLD. On the analog side, a 16-channel 10-bit ADC handles sensor inputs.
The LM3S9B90-IBZ80-C3T is officially classified as Obsolete per the manufacturer's lifecycle record. TI has not published a direct pin-compatible successor for this exact Stellaris part; the Stellaris family was folded into the Tiva C series, but those devices use different package footprints and peripheral maps. If you are still in design phase, a migration to a current TI Cortex-M4F part (such as the TM4C129x series) is worth evaluating, though it will require a board respin.
Stencil aperture should match the ball diameter minus 10% for a clean solder joint.