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How SD card should be powered with TPS65910?

Jiansheng Liu
Intellectual 310 points
Other Parts Discussed in Thread: TPS65910, AM3715, TPS65950, AM3517

I am using TPS65910 with AM3715. A SD card attached to MMC interface of AM3715 will be used as booting source. As the reference design, the MMC/SD interface of AM3715 and the SD card are powered from VMMC rail of TPS65910. However VMMC is default to OFF when it is in AM3715 setting mode (BOOT0/1=10). It means that both MMC/SD interface of AM3715 and the SD card will have no power until TPS65910 is initialized. But the initialization code of the PMIC is located in SD card. So we are in a died loop.

The solution seems to power MMC/SD interface and SD card from a default ON rail, any suggestions about which rail we should use? Only SD card will be used so what we need is a default ON 3.3V rail with at least 150mA capacity.

 

thanks

Jiansheng

 

  • 0
    TI__Genius 15100 points

    Hi,

    VAUX33 is part of the power-up sequence. This supports 150mA.

    Isnt this ok for your use case?

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    Prodigy 90 points

    Hello Gandhar,

    i am a little bit confused about your suggestion in combination with the I/O properties of the AM3715.

    If I use (pullups & VCC) the MMC/SD interface with VAUX33 is the problem, that the MMC1 I/O buffers of the AM3715 are only 3.0V I/O's. In this case, the MMC1 I/O buffer voltage are set with VDDS_MMC1 (pad N24 in CUS package) connected to VAUX33!?.

    The TPS65910 has no 3.0V output voltage on VAUX33 or VMMC. On the AM3715 EVM from Mistral, powered with TPS65950, is the MMC/SD interface powered with VMMC1 (3.0V are possible).

    The figure 1 in the TPS65910 user guide is the next step of confusion. The signal name on VMMC-output is VAUX33 and the signal name on VAUX33-output is VMMC - is this correct...!?

    Another point is, that the SD-card specification allows a maximal current consumption of 200mA.

    My question is: What is the suggested connection for SD-card-booting a AM3715CUS powered with a TPS65910?

     

    Thanks

    Frank

  • 0 in reply to Frank S.
    TI__Genius 15100 points

    Can you refer to the reference design for this processor+PMIC combination - http://designsomething.org/craneboard/w/overview/default.aspx

    This should be helpful. Please let me know if there are more questions related to PMIC.

  • 0 in reply to Gandhar Dighe
    Prodigy 90 points

    Hello Gandhar,

    I know the Craneboard design - this does not apply the AM3715 but the AM3517! The AM3517 has 3.3V I/Os and has not the explained problem.

    In the Craneboard is VAUX33 unused and VMMC used for USB PHY.

    Can you please comment the figure 1 in the user guide (connections on VMMC & VAUX33)

     

    Regards,

    Frank

  • 0 in reply to Frank S.
    TI__Genius 15100 points

    Hi,

    I understand the confusion, sorry for the errors. Actually with TPS65910 you cannot use MMC boot option. With TPS65950 the OMAP ROM code actually configures VMMC via I2C at bootup time. Such a ROM code compatibility is not possible with TPS65910. 

    I will have to remove the VMMC connection and note that mmc boot option is not possible. The voltage levels are fixed in hardware and hence cant be changed. In case you have an eMMC than this boot option may be possible with VAUX33 default ON option.

  • 0 in reply to Gandhar Dighe
    TI__Genius 15100 points

    Can you refer http://www.ti.com/lit/ds/symlink/am3715.pdf

    Table 3-4 mentions that vdds_mmc1 van be 3.3V (nom)