Hello - Looking for some guidance on layer assignment for data lines on a DDR4 chip set. I’ve been all over the internet and found too much info. Can anyone provide something concise. I’ve also rerouted this a couple times and falling a bit behind. I have screenshots of the chips I’m using if that would help.
Thanks, Bruce
Hi Bruce, could you share the screenshots for our team to look at them?
The issue with trying to provide a specific response is that stackup is highly dependent on IC packaging, technologies being used (like HDI or not), and what else you need to connect to the MCU besides the DDR related nets.
I personally have only done one DDR4 layout. Due to my particular restrictions, I could not route signals on the surface and I needed 3 internal signal layers to route everything out (plus additional PWR support). I included GND layers between each signal layers and also included a dedicated multi voltage split PWR layer. I can see depending on the situation, a user might need more that one dedicated PWR layer.
In many cases, the MCU vendor has a eval board or hardware design guide that can be used to help guide you. You might need to ask for this information as it is considered restricted IP and they do not always have it openly accessable for download.
As a side note, the Sierra stackup calculator can also help you try and determine a proposed stackup. Select “I have a complex BGA” option.
Hello Lucy, yes, I can post screenshots. I’ve had to do some re-routing, so it will be a few days before I have things cleaned up. Stay tuned… Thanks.
Tim, are you the same Tim from Altium? I have figured out a path forward. Getting everything routed and length matched is the next challenge. I should be posting screenshots here soon if you want to check those out. Thanks.
I use Altium and I post on the Altium forum, but I am not Altium staff.
Thanks for mention our Stackup Designer! It’s a great tool and we improved it recently, adding more options for different requirements: https://www.protoexpress.com/tools/pcb-stackup-designer/