32 MHz ARM Cortex-M0+ in a 5x5 mm exposed-pad package
The STM32L071KBU3 is a 32-bit MCU from STMicroelectronics' STM32L0 ultra-low-power series, built around the ARM Cortex-M0+ core running at 32 MHz. Peripherals include a 10-channel 12-bit ADC, DMA, PWM timers, and connectivity via I2C, SPI, UART/USART, and IrDA. The 32-UFQFPN package with exposed pad (5x5 mm) suits space-constrained PCBs where thermal dissipation matters.
The 1.65 V minimum supply is lower than many competitors' 1.8 V floor, which matters when the battery is near end-of-discharge. At 3.6 V maximum, the part tolerates a fully charged Li-ion cell without an external LDO.
It is ROHS3 compliant. The base product number STM32L071 covers multiple density and package variants, so a future migration to a pin-compatible sibling (e.g., with more Flash or a different temperature grade) stays within the same family without a PCB spin.
23 I/O in a 32-pin UFQFPN — layout notes
With 23 general-purpose I/O lines, the part covers a UART, an SPI, an I2C, and a handful of PWM outputs or ADC inputs while leaving room for a few GPIOs. The mounting type is surface mount; no through-hole variant exists for this density.