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[FAQ] AM62L ( AM62L32 , AM62L31 ) Why is MMC1 powered by two different voltage supplies, VDDSHV1 and VDDSHV3 ?

Kallikuppa Sreenivasa
Guru**** 188619 points
Part Number: AM62L

Tool/software:

Hi TI Experts,

Could you confirm that the voltage domains are correct for the MMC1_SDCD and MMC1_SDWP pins?  The datasheet shows both MMC0 and MMC2 as having all member pins bellowing to the same voltage domain.  For MMC1 however, the pins are shown split across VDDSHV3 and VDDSHV1

  • 0
    TI__Guru**** 188619 points

    Hi Board designers,

    The logic state of the MMC1_SDCD and MMC1_SDWP inputs to the host must not change when a UHS-I SD Card changes its IO operating voltage. It is not possible to maintain a valid logic state if these signals propagate through an input buffer of a dual-voltage SDIO cell that changes voltage. So, these signal functions are assigned to IOs that do not change voltage. These signals only connect to switches in the SD Card connector, so there is no reason for them to change voltage when the SD Card signals change operating voltage. The MMC1_SDCD and MMC1_SDWP signals should be connected to the SD Card connector switches and pulled high with external pull resistors connected to VDDSHV1. The other MMC1 SD Card signals with pull-up resistors should have their pulls powered by the VDDSHV3 source that dynamically changes voltage. 

    The MMC2_SDCD and MMC2_SDWP pins are powered from the same power rail as the other MMC2 pins. However, you should not use these pins for the MMC2_SDCD and MMC2_SDWP signal functions if you are trying to connect an UHS-I SD Card to MMC2. For this use case, these signal functions would need to implemented using one of the other pin multiplexing options that uses an IO cell powered from a fixed voltage source. The MMC2 assignments are different because we only expected MMC2 to be used with on-board fixed voltage SDIO devices similar to WiFi or Bluetooth transceivers.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Guru**** 188619 points

    Hi Board designers,

    (+) AM62L: AM62L SD Card Boot Compatibility Issue - Processors forum - Processors - TI E2E support forums

    AM62L: AM62L SD Card Boot Compatibility Issue


    When booting from an SD card on the AM62L, compatibility issues have been observed across different brands. For example:

    ​​SanDisk SD cards​​: Some models fail to boot.
    ​​Kingston SD cards​​: Boot successfully.
    ​​Other brands​​: Mixed results—some cards work normally, while others fail to boot.

    When SD card boot fail:

    Yes, this is a known issue, errata is in the process of being updated.  Your observations align with ours, in that several different types of SanDisk cards fail, while cards from other manufacturers boot successfully.  For silicon revision 1.0, there is not a robust workaround, other than to continue using the working cards.  We have also seen that if you set both primary and backup to SD card boot, sometimes the backup boot will be successful on certain card that failed the primary boot. 
    Regards,
    Sreenivasa