SDMMC and GbE performance versus VDD

[gil_he]

hello,

We are designing with the OSD32MP153C-512M-BAA (the prototypes will have OSD32MP157C-512M-IAA).
The VDD voltage in the SiP sets the I/O voltage of the STM32MP15x (in addition to other circuitry) and in particular the I/Os that are used for the eMMC Flash and RGMII interfaces.
I would like to use a VDD of 3.3V.
As far as I understand, this will limit the performance I can get from my eMMC Flash to DDR52, according to “Table 402. SDMMC operation modes e•MMC in RM0442 Reference manual STM32MP153” (attached).
The table states 3V. I guess 3.3V is also fine.
So, for HS200 I will need signaling voltage of 1.8V, thus VDD of 1.8V.
This will affect all the I/Os voltage of the entire SoC GPIOs, JTAG bus voltage, not-activating the VDDA1V8_REG (bypassing it), etc.

Am I correct?
Can anyone comment or add anything on that?

In addition, I want to use the GbE RGMII interface.
Do I require a VDD of 1.8V for that?

If VDD of 1.8V is required, how will that affect the design?
I am aware of bypassing REG1V8 (connect BYPASS_REG1V8 to VDD) and connecting VDD (1.8V) to VDDA1V8_REG pin.
Anything else?

Thank you
Gil

• This topic was modified 2 years, 11 months ago by gil_he.
• This topic was modified 2 years, 11 months ago by gil_he.

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[Neeraj Dantu]

gil_he,

You are correct that you will need to set VDD to 1.8V in order to make use of HS200 mode for eMMC. Please see https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf for details. Please make sure that you will need this performance as most applications do not require the HS200 mode.

You will not need VDD as 1.8V for Gig LAN implementation. Please see https://octavosystems.com/octavo_products/osd32mp1-red/ for a reference implementation of RGMII with 3.3V as VDD.

Looks like you have taken a look at https://octavosystems.com/forums/topic/procedure-for-configuring-vdd1-8v/. The post describes all the configuration required for 1.8V IO.

Best,
Neeraj

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