STM32MP157 SDcard level shifter

[NCF]

Hi guys,

The schematics for STM32MP15x-EVAL board (MB1263) uses a level shifter for SDcard from NXP (IP4856CX25) that is now obsolete.

I found 2 close alternatives:

• ST6G3244MEBJR from ST, with one pin only (C4) different from IP4856
• TXS0206YFPR from TI, with 5 pins less then IP4856

Questions:

1. Is it possible to use the ST6G3244 from ST replacing the IP4856CX25 from NXP? If so, is it a direct replacement (with pin C4 of STG3244 tied to GND)?
2. I noticed that the NXP part has a wider host side voltage range up to 3V3 than the ST part. I don't have the MB1263 board here to measure, so I need to know what is the Voh of the SDcard lines in STM32MP157 in MB1263. Can anyone help me on this?
3. Is it possible to use the TXS0206 from Texas which have a wider host side voltage range compatible with 3V3?
4. Is there any other alternative to replace the IP4856CX25 from NXP?

Thank you guys in advance for any light on this topic.

[PatrickF · Accepted solution]

ST6G3244MEBJR is a possible solution, only when STM32MP15x is using VDD = 1.8V.

TXS0206YFPR is functionally ok (although need an external 1.8V/3V supply for card side IO voltage if you want to use UHS-I), but seems not to support DDR50 (which need 100Mbps data rate per pin).

Most SD-Card level shifter are intended for 'portable device' market, and so, target usually 1.8V IO on host side.

If you use STM32MP15 with VDD=3.3V, only possible solution is to skip level shifter and stick to 3.3V SD-Card mode (i.e. High-Speed mode, which is 25MBytes/s for a 50MHz clock). Depending on your use case, this is usually good enough.

[NCF]

Thank you for your prompt reply.

I'd like to ask you one more question, if you don't mind.

In document "en.MB1263-C01_schematic.pdf" - which I'm using as reference for my own board - on page 5 the PMIC is shown with several outputs labeled with no voltage figures. Where can I find info on those voltages?

[PatrickF]

Here is some link which could help you:

Wiki page related to supplies https://wiki.st.com/stm32mpu/wiki/Regulator_overview

STPMIC1 datasheet https://www.st.com/resource/en/datasheet/stpmic1.pdf

AN5031 https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf

Wiki page related to board customization https://wiki.st.com/stm32mpu/wiki/How_to_create_your_board_device_tree

[CKUND.1]

ST6G3244MEBJR and TXS0206YFPR are clock limited at 60Mhz. The obsolete IP4856CX25 is 208Mhz

So if I not wrong, you cannot use SDR50 and SDR104 bus speed modes.

I have the same issue about the STM32H757 and Sandisk Extreme Pro card UHS-1.

I would like to get high speeds, but unfortunately seems that we don't have fast level translators actually.

It is maybe because MPUs could be powered with 1.8V, but in the case of STM32H757 I need to use 3.3V.

I am a little frustrated. STM32H757 seems so modern, but the SDMMC interface work with older specifications than moderns eMMC and SDCards selling on market.

[NCF]

NXP has a new level shifter that can handle SDR104 (208MHz): NVT4857UK

The good news is that it's in production. The bad news is that it's only 1V8 at host side.

Like PatrickF said, the 3V3 host is not the focus for this type of level shifter anymore...

I switched the I/O voltage to 1V8 to use the ST6G3244 from ST.

[CKUND.1]

Take a look in this part number. For MPU maybe help you

NVT4857UK from NXP

[GreenGuy]

I would like to pose a question for clarification.

Given that the same IP4856CX25 is used on the STM32H734-Eval board that is running on 3.3V, what good is it doing there if the only possible solution for 3.3V systems is to not use a translator?