Hi everyone,

I’m working on a custom PCB design and want to implement a microSD card connected to an STM32H745 microcontroller via the SDIO interface.

While reviewing reference schematics, I noticed that in some designs a level shifter for 1.8V is placed on the SDIO lines between the microcontroller and the microSD card.

Could someone please explain:

1. Why is a level shifter needed in this case?
2. Can I implement the microSD connection without using a level shifter, and just connect the SDIO lines directly to the STM32H745?

Any insights or best practices would be greatly appreciated!


Thanks in advance

 

Hi everyone,

I’m working on a custom PCB design and want to implement a microSD card connected to an STM32H745 microcontroller via the SDIO interface.

While reviewing reference schematics, I noticed that in some designs a level shifter for 1.8V is placed on the SDIO lines between the microcontroller and the microSD card.

Could someone please explain:

1. Why is a level shifter needed in this case?
2. Can I implement the microSD connection without using a level shifter, and just connect the SDIO lines directly to the STM32H745?

Any insights or best practices would be greatly appreciated!


Thanks in advance

SD cards default to 3v3 but UHS-I and above use 1v8 for all high speed modes. Only legacy cards do I/O at 3v3. You would probably find reading the standard (or probably the Wikipedia article) would be helpful.