SPRADO8A March 2025 – May 2026 AM62L
The recommendation is to provide provision for a software-enabled (controlled) power switch (load switch) that sources the power supply (VDD) to the SD card. A fixed 3.3V supply (processor IO supply) is connected as the input to the power switch.
Use of power switch allows power cycling of the SD card supply (since resetting the power switch is the only way to reset the SD card) and resetting the SD card to the default state when UHS-I SD card is used.
The recommendation is to implement the SD card power switch enable and reset logic using a 2-input ANDing logic since the ANDing logic provides flexibility to be able to reset the attached device in all processor reset condition including local reset (in use cases where the attached device becomes non-responsive and needs to be reset without a power cycle). Processor GPIO is connected as one of the input to the AND gate with provision for pullup (10kΩ or 47kΩ) (to support SD card boot) near to the ANDing logic AND gate and provision for 0Ω to isolate the GPIO output for testing or debug. The other input to the AND gate is the MAIN domain warm reset status output (RESETSTATz).
The external power switch sourcing the SD card power supply is recommended to default to ON (powered state) to support SD card boot.
For implementation, see the processor-specific EVM.