DRAM Modules FAQs

Can Vtt and Vref be supplied by the same supply in my system design?
With proper decoupling this can be an acceptable design. However, Micron recommends ensuring all supplies are separated. VTT tends to have more noise on it because it supplies signals that are regularly switching. A robust design would typically not connect these supplies due to the possibility of introducing this noise onto the Vref plane which should be as stable as possible. Additionally, Vref requires much less current than Vtt.

Is there a set of trace lengths and routing rules that are standard for use when designing a system that uses a specific module technology and form factor?
No. A robust memory subsystem design that includes the use of 1 or more memory modules must be simulated in order to determine the optimum trace lengths, terminations. However, our design guides such as TN-47-01 and TN-41-08 have some best practices and design examples based on some typical system assumptions. This information is not meant to be the only way your system can be designed. It is a starting point and moreover an example of the steps used to determine the best design for your system.