It packs a single-core Cortex-M4 with DSP and floating-point instructions into a 49-ball WLCSP (2.97x2.97 mm) — the kind of package you spec when board area is the tightest constraint, like a wearable, a sensor module, or a portable medical probe.
84 MHz, 512 KB Flash, 96K RAM — the BOM-fit tier
The 36 I/Os and connectivity set — I²C, SPI, UART/USART, USB OTG, SDIO — cover most sensor-fusion and human-interface designs.
For ongoing production, secure your last-time-buy quantities or plan a pin-compatible migration.
WLCSP footprint — what the reflow line needs to know
That means the MSL rating (typically MSL 1 or MSL 3 for this package type) must be confirmed before the reel hits the oven; a high-MSL part that skipped the bake will popcorn. The 0.4 mm or 0.5 mm ball pitch demands a fine-feature stencil and tight solder-paste volume control.