How do you handle length matching constraints for data and clock lines in DDR5 routing?
In DDR5 design, length matching between data lines and DQS is extremely critical. What are some practical layout techniques for handling this?
2Answer
High-frequency discrepancies are typically caused by the following: 1 Material parameters (Dk/Df) not accurately modeled for frequency dependence; 2 Conductor surface roughness model not enabled; 3 Inconsistent port calibration reference planes. First, verify material settings and enable the Huray roughness model, then compare simulated and measured group delay.
Additionally, verify that the mesh is sufficiently fine. At high frequencies, the skin depth decreases, so ensure there are at least 3 to 4 mesh layers across the conductor cross-section. Also, placing radiation boundaries too close to conductors can introduce errors.
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