What this Stellaris MCU brings to the board
The LM3S5D91-IQC80-A2T is a 32-bit ARM Cortex-M3 microcontroller from the Stellaris 5000 series, clocked at 80 MHz. It has 512 KB Flash and 96 KB RAM.
512 KB Flash — firmware fit and field updates
The 512 KB Flash is sized for a mid-complexity firmware image: a bootloader, a real-time kernel, communication protocol stacks (CANopen, USB device), and application code. The Flash is programmable in-system, so field updates are possible over the USB or CAN link. No EEPROM on-chip; if you need non-volatile parameter storage, budget a few Flash pages for emulated EEPROM or add an external serial EEPROM.
Connectivity and I/O lineup
This MCU includes CANbus, USB OTG, and serial interfaces (UART, SPI, I²C, SSI, Microwire, IrDA, LIN). The 72 GPIOs can drive a keypad-and-LED panel plus a parallel bus.
Obsolete — sourcing reality
The LM3S5D91-IQC80-A2T is officially obsolete per the manufacturer. No last-time-buy window remains open. For a BOM line that needs this exact order code, the only channel is the independent surplus and broker market. We source and quote this part to order against an RFQ — availability and current pricing are confirmed at quote time. There is no direct pin-compatible drop-in from TI's current portfolio; the Stellaris line was absorbed into the Tiva C series, but those parts differ in peripheral map and require firmware porting. If you need a drop-in second source, check the LM3S5D91's siblings in the same 100-LQFP package — the base part number LM3S5D91 covers multiple speed and temperature grades, but all are now obsolete.