Other Parts Discussed in Thread: TPS22965, TMDSEVM572X
Hi,
We have observed that there is difference in implementation of the SD card (MMC1) interface circuit between AM572x GPEVM and Vayu EVM. Based on this we have the following queries.
1. On AM572x GPEVM, LDO1 output of the PMIC (TPS6590374ZWSR) is used as the power source for VDDSHV8 (MMC1 power group) pins of the processor and also the VDD supply to the SD card (via the connector). The maximum current capacity of this LDO is 300mA. However the maximum current required for VDD supply of SD card (as per the SD specifications version 3.01) in the 1.8V signaling modes like SDR104, SDR50 for SDHC & SDXC cards exceeds the current limit of LDO1. Are these modes tested on the SD card interface of the EVM?
2. On Vayu EVM, LDO1 output of the PMIC (TPS659039) is used as the power source for VDDSHV8 (MMC1 power group) pins of the processor. The VDD for the SD card is sourced by the 3.3V supply generated by the external SMPS- TPS43351QDAPRQ1 via two load switches. In this case the VDD is fixed to 3.3V. Can this scheme support 1.8V SD signaling modes on Vayu EVM? Are these modes tested on the EVM?
Based on the above two queries, which scheme should be implemented to support 1.8V SD signaling modes?
Note: On Vayu EVM, the 3.3V output generated by the external SMPS is connected to the first load switch (TPS22965) which is enabled by the GPIO_4/SYSEN1 output of the PMIC. The output of this load switch is fed to the second load switch which is enabled/disabled via I2C read/write. The output of the second load switch is connected to the VDD input of the SD card.
Regards,
Prachi
