It runs at 48 MHz, carries 32 KB of Flash and 4 KB of RAM, and brings 18 general-purpose I/O plus a 10-channel 12-bit ADC. The part lives in a 20-ball WLCSP (1.99×1.94 mm) — that footprint is the whole story: you pick this MCU when board real estate is the tightest constraint and a few millimetres decide the layout.
Connectivity covers I2C, SPI, and UART/USART, enough for a local sensor bus or a serial link to a host controller.
Package reality — WLCSP handling
The 20-WLCSP (1.99×1.94 mm) is a wafer-level chip-scale package with no mould compound. PCB pads must match the ball layout exactly; rework is not trivial.