The LM3S5739-IQC50-A0: That means TI has stopped actively promoting it for new projects, though it remains available for existing production runs through the independent distribution channel. For a sustainment program or a repair depot that already has this MCU in the BOM, the supply path is surplus and broker inventory — not direct factory allocation.
This is narrower than the 3.3 V typical for most Cortex-M3 parts, so the board-level regulator needs to be a 2.5 V LDO or a buck converter set to 2.5 V with ±5% tolerance. A 3.3 V system will need a separate 2.5 V supply for this MCU; the I/O pins are not 5 V tolerant.
100-LQFP footprint and layout notes
The 100-LQFP package is 14x14 mm. Surface-mount only.