STM32h743 max FMC SDRAM clock 100MHz?

[Dat Tran]

Hi,

I found this in datasheet

 

But we config SDRAM at 120MHz, because we are running at 480MHz.

(480MHz / 2 / 2 = 120MHz).

I am thinking the datasheet is for STM32H7xx 400MHz, because when I config SDRAM at 120MHz, the system works fine without issue.

Does max 100MHz FMC clock apply for STM32H7 480MHz?

Thanks.

[KDJEM.1 · Accepted solution]

Hello @Community member​ ,

There are two STM32H743 revisions: Rev.V and Rev.Y.

For that, the SDRAM Max clock frequency is 110MHz for Rev.V and 100MHz for Rev.Y in the interval of 2.7V to 3.6V.

The FMC_SDCLK we can run SDRAM depends on the VDD and on the capacitor value.

For more explanation, I advise you to take a look at DS12110 and precisely 7.3.17 FMC characteristics Section.

When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

Thank you.

Kaouthar

[Tesla DeLorean]

No physical damage occurs when you exceed the limit. But it depends on the characteristics of the IO cells and load capacitance of the traces/device attached. It might work, they just don't guarantee it across their process window (how the wafers are diffused)

It's why they have a DIV3 option

[SofLit]

Hi,

As stated by @KDJEM.1 the Max frequencies are provided in the DS. But if you want to run at 480MHz with the FMC max frequency you can use different PLLs for the CPU and FMC.