Key design implications (schematic + PCB)
- Interface choice: the host must support either SDIO (4-bit) or SPI mode.
- Voltage levels: most microSD runs I/O at 3.3 V (some hosts use 1.8 V signaling for high speed). You must match what your host supports.
- ESD protection: add ESD on the card-facing lines (CLK/CMD/DATx) and the connector shell.
- Power switching: it’s common to add a load switch (or at least a ferrite + decoupling) so you can power-cycle the card.
- Layout: keep CLK/CMD/DAT short, matched where needed, and avoid stubs; place the connector at the edge with a solid ground reference.