What this part is and where it fits
The Texas Instruments LM3S801-IQN50-C2T is a 32-bit ARM Cortex-M3 microcontroller from the Stellaris® 800 series, running at 50 MHz. It packs 64 KB of Flash program memory and 8 KB of SRAM, with 36 general-purpose I/O lines. On-chip peripherals include I²C, SPI, SSI, UART/USART, a quadrature encoder interface (QEI) for motor position feedback, PWM outputs, and a watchdog timer — all powered from a 3 V to 3.6 V supply. The internal oscillator keeps the BOM simple. Rated for -40°C to 85°C, it fits industrial control panels, motor drives, sensor nodes, and embedded automation where a mid-range Cortex-M3 with a modest memory footprint is the right fit.
50 MHz core — what it means for the control loop
At 50 MHz, the Cortex-M3 single-cycle multiply and hardware divide handle PID loops, encoder decoding, and Modbus packet parsing without a separate co-processor. The 8 KB RAM is enough for a few hundred bytes of stack and a moderate-size buffer; if your application needs larger data arrays or a real-time OS with multiple tasks, the 8 KB ceiling will be the first constraint you hit.
NRND — plan the BOM transition
The LM3S801-IQN50-C2T carries an NRND (Not Recommended for New Designs) status. It may still be available through the independent channel for existing production runs.
The 48-LQFP (7x7 mm) package is a common footprint for mid-density MCUs; it routes easily on a two-layer board. The -40°C to 85°C temperature grade covers most industrial and outdoor telecom enclosures without a heatsink. Brown-out detect and POR are built in, so an external supervisor IC is optional unless you need a precise reset threshold.