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AM4376: Low Voltage SD Card interface at MMC0

Josko M
Intellectual 830 points
Part Number: AM4376

Hi,

we would like to implement 1.8V low voltage signaling (LVS) interface for SD card at MMC0 and also use this SD Card interface as a bootable medium during the board bringing . 

Also we would like to use it in MMC/SD 4-bit mode.

Following pins are mapped to the VDDSHV1 power bank: 

D1: MMC0_CLK

D2: MMC_CMD

C1: MMC_DAT0

C2: MMC_DAT1

B2: MMC_DAT2

B1: MMC_DAT3

Is it enough just to switch the VDDHV1 bank to 1.8 V power rail in order to support 1.8V low voltage signaling (LVS) interface SD Cards?

According to the data sheet, chapter 5.12.17.1 MMC Electrical Data and Timing, AM4376 should support 1.8V signaling for SD cards, correct?

What should we take care about linux image in order to support 1.8V signaling SD cards? 

Up to now we have been using VDDHV1 bank at 3.3V. 

The SD card we would like to use it: i300 microSDXC Card (mouser.at)


Regards 

 

  • 0
    TI__Guru 55425 points

    The IOs implemented on AM4376 do not support dynamic voltage change. The IO supply must be within the 1.8V Recommended Operating Condition range (ROC) or the 3.3V ROC range before the device is released from reset. The IO voltage is locked to the initial voltage applied to the power rail once the device is released from reset. Therefore, the IO power rail must not change while reset is de-asserted. This prevents AM4376 from supporting the higher operating speeds provided with UHS-1 SD Cards since these cards begin communications at 3.3V and change to 1.8V after the host negotiates a IO voltage change with the SD Card.

    Operating the IOs at a fixed 1.8V is not a problem, but the MMCSD host controller implemented in AM4376 was designed long before the LVS standard was defined, so the host controller does not support the handshake requirements defined in the SD Card Specification Low Voltage Interface Addendum.

    Regards,
    Paul