About pin package delay for STM32MP1 when doing DDR3 routing

[diverger]

Hi,

I find the 'STM32MP1_SeriesDDRmemory_routing_guidelines_layout_examples_V3.0' from ST's site.

I've several questions:

1. It seems the column 'STM32MP15XXAA LENGTH (mm)' is the package delay per pin, right?
2. Actually, the delay is a time factor. But here the delay is given in 'mm', then what's the propagation speed ST used?
3. Can you provide delays in ps? Or can I get the delays from the IBIS file?

Thanks.

[PatrickF]

Hi @diverger​ ,

actually, the values in the table are track lengths, so in mm. This values are provided to compensate for package internal track length differences.

Did you have a look to AN5122 ? Excel table is providing also a quick colored check by entering your PCB extracted track length.

I have asked experts to see if they can provide the propagation constant which should be used for the package, but I think the possible time delta versus basic FR4 is probably to be neglected Vs the time delays on your board.

At least many customers using DDR3L have not face issues by following AN5122 or using example routing provided in the ZIP file.

Regards.

[Prashanth]

HI @PatrickF ,

I am working with stm32mp157, in AN5122 it is mentioned that we have to consider MPU package delay for ddr3 memory (I am using DDR3L memory by micron).

I wanted to know that where can I find the package delay and length equalization table, as it is not provided in AN5122.

Thanks.