The STM32F405OEY6TR is an STMicroelectronics STM32F4-series MCU built around an ARM Cortex-M4 core running at 168 MHz. It packs 512 KB of Flash and 192 KB of SRAM, giving you enough code space for a real-time control loop with a moderate protocol stack and a few kilobytes of data buffers. The 168 MHz clock is the key differentiator from the lower-speed STM32F1 or STM32L1 families — if your application needs single-cycle MAC or hardware FPU for sensor fusion or audio processing, this core delivers it without a separate DSP. The 90-WLCSP package (4.22 x 3.97 mm) is the smallest footprint in the STM32F405 line. The 72 I/O pins break out most of the peripheral set: two CAN 2.0B interfaces, a USB OTG port, multiple SPI/I²C/UART channels, and an I²S audio interface.
Industrial temperature range — where this MCU fits
It is not AEC-Q100 listed, so it is not the pick for under-hood automotive or engine-bay environments — stay with the STM32F4 automotive-grade variants for that.
ST continues to manufacture the STM32F4 series, and the part is ROHS3 compliant. For a production BOM this means no forced redesign cycle from obsolescence — the risk is the usual allocation pressure on 90-WLCSP packages during tight supply periods.