What this MCU is and where it fits
The LM3S5K36-IQR80-C3: The LM3S5K36 is a 32-bit ARM Cortex-M3 microcontroller from the Texas Instruments Stellaris 5000 series, clocked at 80 MHz. It packs 128 KB of Flash and 24 KB of RAM, plus CAN, USB, I²C, SPI, SSI, UART, and IrDA connectivity.
80 MHz — what that means for the BOM
80 MHz is a mid-range operating point for a Cortex-M3. It gives you enough throughput for a real-time control loop with sensor polling and a CAN message stack running concurrently, but it is not a high-end part for heavy DSP or graphics. The internal oscillator keeps the BOM simple — no external crystal needed if the timing accuracy is within the internal RC tolerance.
Memory and peripherals — sizing the design
128 KB of Flash and 24 KB of RAM fit firmware for a CANopen or Modbus node with a modest data table. The 8-channel 10-bit ADC handles analog inputs like potentiometer feedback or current-sense voltages. The 33 GPIOs cover a small keypad, a few LEDs, and the bus transceiver control lines. If your application needs more than 24 KB of working RAM for buffering or a larger protocol stack, this part will run out of headroom.
Obsolete — sourcing reality
The LM3S5K36 is marked obsolete by Texas Instruments. No last-time-buy window remains open through the franchised channel. For a BOM line that requires this exact order code, the only supply path is the independent surplus and broker market.