48 MHz Cortex-M0 in a 5x5 mm package
This is the value-line member of the STM32F0 family, aimed at cost-sensitive control applications where the peripheral set (I²C, SPI, UART, LIN, HDMI-CEC, plus DMA and PWM) covers sensor aggregation, motor control, and human-interface tasks without overprovisioning.
The internal oscillator trims out the external crystal for many UART and I²C baud rates, saving two pins and a few cents on the BOM.
Listed as Active by ST. ROHS3 compliant. For production BOMs this means no forced redesign cycle from obsolescence — ST continues to manufacture and support the STM32F0 series.
13-channel 12-bit ADC and one 12-bit DAC
The ADC is enough for reading multiple analog sensors (thermistors, potentiometers, current shunts) without an external mux.
Second-source gate: STM32L151CBU6A
The STM32L151CBU6A is a functional cousin — same 32-bit ARM core (Cortex-M3 vs M0 here), same Flash density, but runs at 32 MHz and draws lower power. It swaps the UFQFN for a Tray package and adds USB connectivity. The STM32F051K6U7TR is the higher-speed, lower-cost option for designs that don't need USB and can tolerate the M0's smaller instruction set. Pin compatibility is not guaranteed — the series uses a different pinout and supply scheme.