Cortex-M3 at 80 MHz — flash and RAM headroom for control applications
The LM3S1G21-IQC80-A2 is a Texas Instruments Stellaris ARM Cortex-M3S 1000 series microcontroller built around a 32-bit ARM Cortex-M3 core clocked at 80 MHz. The 80 MHz clock rate on the Cortex-M3 delivers roughly 1.25 DMIPS/MHz, so the core throughput sits around 100 DMIPS — enough to handle a PID loop at several kilohertz while servicing UART and SPI interrupts without dropping characters. The 64 KB SRAM leaves about 40 KB free after a typical RTOS and HAL footprint, which is comfortable for a moderate data buffer or a small frame grab.
The peripheral mix includes EBI/EMI for external memory or FPGA glue, plus I²C, SPI, SSI, UART/USART, IrDA, LINbus, and Microwire serial interfaces — enough to talk to a CAN transceiver, an external ADC, a display controller, and a few sensors without needing a CPLD for port expansion. On-chip analog is an 8-channel, 12-bit ADC — useful for reading potentiometer feedback, current-sense resistors, or thermistor inputs in a control loop. The internal oscillator saves a crystal on the BOM, though the accuracy is adequate for UART timing but not for a precision time base. Additional on-chip blocks include brown-out detect, POR, DMA, PWM, and a watchdog timer. The DMA engine can move ADC results to RAM without CPU intervention, which keeps the core free for the control algorithm.
Board assembly requires a controlled solder profile — the fine pitch means the stencil aperture and paste volume need to be dialled in for consistent solder joints. The package body is 14x14 mm, so it fits on a standard 4-layer PCB with fan-out vias under the body.
Texas Instruments lists the LM3S1G21-IQC80-A2 as Obsolete. The Stellaris family was acquired by TI in the Luminary Micro acquisition and has been superseded by the Tiva C series and later Cortex-M4F parts. We source it to order against an RFQ — quantities are lot-specific, and we confirm authenticity, date code, and condition at quote time. If you have a BOM line that still calls out this order code, we can quote it; if you are starting a new design, this is not the part to build into a new board.