Help choosing the best external RAM for STM32H723

[elso]

Hi all!

I am making a PCB with STM32H723, and have chosen this MCU due to its greats specs and versatility. However I would like to add at least 4Mbit (0.5MB) of RAM, either as SDRAM, SRAM or PSRAM etc. using the FMC (Flexible memory controller). 

However I am lost in the process of choosing the best possible external RAM for this MCU.

I want to achieve the highest memory transfer speed, but it needs to be compatible with the STM32H723. I see there are technologies like HyperBus and OctoSPI, but I assume parallell is the best. In the .ioc file, the FMC can be configured to run at 275 MHz, but I don't know if that is realistic to achieve reliably.

I can see that in this youtube video https://www.youtube.com/watch?v=h28D4AaPSjg the achieved frequency is 95 MHz, but using a SDRAM which in theory have lower performance than SRAM or PSRAM. Any suggestions of a great RAM for my purpouse?

If anyone have some feedback or tips, I would appreciate it! 

[FBL]

Hello @elso 

You can get inspired with the reference board provided like STM32H735G-DK. You can check FMC interface connectivity and signal layout guidelines in AN5419. 

The choice depends on the application specific requirements: the required transfer speed, available pins, and noise immunity. The advantage of parallel interface is the transfer bandwidth and supports the Memory mapped mode and XIP byte access. However, it costs higher number of pins making hardware design more complex.