Question, changing eMMC power supply voltage, i.MX6SX

[SLICE]

Dear team,

I would like to ask about eMMC power supply connected to i.MX6SX.

My customer plans to use i.MX6SX, and they want to add a feature of changing eMMC operation voltage 3.3/1.8V on their proto-board.

Could you show me whether any problem in the following idea?

They believes that they can connect SDx_VSELECT pin of i.MX6SX to Power switching IC, and Power supply flows out from the Power Switching IC can be connected to NVCC_SDx of i.MX6 and to VCCQ pins of eMMC.

Please find the attached file for the diagram.

(1) Is the above correct?

(2) And could you show me whether they can use GPIO pin instead of SDx_VSELECT pin in the above?

(3)

They want use SD3 or SD4 port for the eMMC connection, but they find there is no VSELECT pad for SD3 port. In the case of using SD3 port for eMMC connection, is it possible to use GPIO pin (like using SD4_SELECT for SD4 port) to change the power supply voltage of eMMC for selecting voltages?

Thanks,

Miyamoto

[weidong_sun]

Hello Miyamoto,

  According to your application, see following advice, please!

SD3 & SD4 port can be supplied by 3.3V or 1.8V power.

---SD3 port.

   From schematic of EVK, see page 6, there are 2 PINs for power input of SD3 port, one is NVCC_HIGH(3.3V), the other is NVCC_LOW(1.8V).  So you can supply NVCC_SD3 with 3.3V and 1.8V at the same time, don't need to use a switch for voltage selection.

---SD4 Port

  There is only one PIN for SD4 power input, NVCC_SD4, 3.3V or 1.8V can be input here. Due to only one PIN, you can use a switch to select voltage.

   In my opinion, if you only use one eMMC chip on your board, better option is to connect it to SD3 port. it will make  cost down(don't need a switch)

   In addition, you should pay attention to Boot mode configuration, see page 339 of reference manual, BOOT_CFG2[1] is used to select voltage of SD3(3.3V or 1.8V), research page 21 of schematic, please! it can also help understand your application.

have a nice day!

TIC Weidong Sun

[SLICE]

Hello weidong.sun‌

Thanks for your kindly explanation.

I might understand why VSELECT pin for SD4 port exists and it does not exist for SD3.

Can I understand that the customer’s idea around their design is correct? (the attached file)

And can I understand that one can use GPIO pin for switching voltage for SD3 or SD4 port?

Best Regards,

Miyamoto

[weidong_sun · Accepted solution]

Hello Miyamoto,

    Did you notice R93 is DNP(Do Not Place)? It means NVCC_3V3 is default input, if you want to use NVCC_1V8, R93 should be populated, and R92 is depopulated.

    SD4_VSELECT is not connected to other devices on schematic, I checked the customer's design you attached, and I think the design is not correct. Because GPIO should be controlled to output HIGH or LOW level by software, how to ensure correct voltage is selected before bootloader is loaded by ROM CODE?

     Customer can design it like this:

Hope my advice can help you!

Have a nice day!

Best Regards,

TIC Weidong Sun

[SLICE]

Hello weidong.sun‌

Thanks for your support!

Here is some additional questions from the customer.

(Should I create a new thread?)

In the case of using SD3 port for connecting to eMMC, my customer has a concern on the deviation of the timing between a changing the voltage of eMMC power supply and a changing i.MX6SX’s internal operation voltage.

(1)

Are there any ways to detect the voltage change of eMMC has been actually completed?

(2)

In the case of using SD4 port;

Can I understand that the timing deviation such as above does not occur by using SD4_VSELECT pin for changing eMMC voltage?

Best Regards,

Miyamoto

[SLICE]

Hello weidong.sun‌

Sorry for hurrying you up, but can i have your comments?

BR,

Miyamoto

[SLICE]

Hello weidong.sun‌

I created new thread as below.

https://community.nxp.com/thread/453254 

Please give your answer to that.

Best Regards,

Miyamoto

[weidong_sun]

OK, got it!

Best Regards,

Weidong