Low-power ARM Cortex-M0+ in a 5x5 mm BGA
The STM32L051R8H6TR is a 32-bit ARM Cortex-M0+ MCU from ST's STM32L0 ultra-low-power series, clocked at 32 MHz. It packs 64 KB of Flash program memory, 8 KB of SRAM, and 2 KB of embedded EEPROM, all in a 64-ball TFBGA package measuring 5x5 mm. The supply range spans 1.65 V to 3.6 V, letting it run directly from two alkaline cells or a single Li-ion cell down to near-discharge voltage without a boost converter. Fifty GPIOs, a 15-channel 12-bit ADC, and serial interfaces (I²C, SPI, UART/USART, IrDA) make it a fit for sensor hubs, portable instruments, and battery-powered control nodes where board area is tight.
Memory map and field-update reality
The 64 KB Flash is enough for a modest application stack — a bootloader, a real-time scheduler, and a few hundred lines of sensor-fusion code — but leaves little headroom for over-the-air update images if you need dual-bank swap. The 2 KB EEPROM emulated in Flash (or the dedicated 2 KB true EEPROM block) handles calibration constants and fault logs without wearing the main program store. With 8 KB RAM, you are not running a TCP/IP stack with large buffers; keep DMA transfers under 2 KB to avoid heap fragmentation.
Industrial temperature and package constraints
Rated for -40 to 85 °C ambient. The 64-TFBGA package (5x5 mm body) requires a controlled reflow profile and X-ray inspection after assembly.