SPRZ452I july 2018 – may 2023 AM6526 , AM6528 , AM6546 , AM6548
IO, MMCSD: Incorrect IO Power Supply Connectivity Prevents Dynamic Voltage Change on VDDSHV6 and VDDSHV7
AM65x SR 1.0
The LVCMOS IOs associated with device pins MMC0_SDCD (A23) and MMC0_SDWP (B23) receive power from VDDSHV6 rather than VDDS_OSC1.
The LVCMOS IOs associated with device pins MMC1_SDCD (B24) and MMC1_SDWP (C24) receive power from VDDSHV7 rather than VDDS_OSC1.
VDDSHV6 and VDDSHV7 also provides IO power to MMCSD0 UHS-I PHY and MMCSD1 UHS-I PHY, respectively, which may require dynamically voltage change for some use cases.
LVCMOS IOs detect the voltage applied to their respective VDDSHV power rail while MCU_PORz or PORz reset inputs are asserted to determine if they should operate in 1.8 V mode or 3.3 V mode. The IO voltage operating mode is latched on the rising edge of PORz.
After PORz is de-asserted, VDDSHV6 and VDDSHV7 must remain within the recommended operating range of the applied voltage to avoid potential long term reliability issues.
Since VDDSHV6 and VDDSHV7 shall not change after PORz is released, it is not possible to implement dynamic IO voltage change on the IOs associated with MMCSD0 and MMCSD1.
Advisory i2026 describes a reliability issue when operating VDDSHV6 and VDDSHV7 at 3.3 V, which limits the operation of these IO supplies to 1.8 V.
These four LVCMOS IOs associated with VDDSHV6 and VDDSHV7 should have been powered from VDDS_OSC1, which is a fixed 1.8 V supply.
For most applications where MMC card detect and/or write protect function is implemented on these pins, the external pull-up resistors associated with these signals need to be powered from the same power source as the respective VDDSHV6 or VDDSHV7 power pins.
For these use cases, PCBs designers should consider including resistor installation options that allow external pull-ups to be powered from the respective VDDSHV6 / VDDSHV7 supply or the VDDS_OSC1 supply. The resistor installation option allows a common PCB design to support current silicon revision and future silicon revisions where these IOs will be powered from VDDS_OSC1.
For use cases other than MMC card detect and write protect, the effect of this IO being sourced from a different supply rail needs to be evaluated/considered for any connectivity to these pins.