FMC SDRAM design recommendations (STM32F446)

[Rihem_]

Hello,

I am designing a board with a STM32F446 connected to an IS42S16160H SDRAM through the FMC interface.

Could you please provide ST’s official recommendations regarding the use of series resistors on FMC lines?

• Typical values (22–33 Ω)?

• Any ST guideline or application note available?

Thanks,

Rihem

[ELABI.1 · Accepted solution]

Hi @Rihem_,

You can take a look at these guidelines for the FMC interface in this Application Note AN4488:

In these guidelines, it is not recommended to use series resistors if you ensure that the transmission line (trace) on the PCB has a controlled characteristic impedance around 50 ohms.

However, if you need further optimization for the signal integrity, you can use series resistors. To determine the exact value, you need to perform a simulation using the IBIS models of the STM32F4.

For this purpose, you can refer to Application Note AN4803, which contains an example showing how to perform a simulation with HyperLynx on an MCU for SDRAM memory using the FMC controller, specifically in section 5.1 HyperLynx simulation with SDRAM.

This is the link to download the IBIS models for STM32F4 to use in your simulation

Thanks.

ELABI.1