SPRAD66B February 2023 – December 2024 AM62A3 , AM62A3-Q1 , AM62A7 , AM62A7-Q1 , AM62D-Q1 , AM62P , AM62P-Q1
For a PCB design, portions of the DDR signal traces are microstrip (BGA break-out segments), but majority of the trace segments are stripline (internal layers). Even though there is a wide variation in the proportion of track length routed as microstrip or stripline, the length or delay matching process must include a mechanism for compensating for the velocity delta between these two types of PCB interconnects. A compensation factor of 1.1 has been specified for this purpose by JEDEC. All microstrip segment lengths are to be divided by 1.1 before summation into the length matching equation. The resulting compensated length is termed the stripline equivalent length. While some amount of residual velocity mismatch skew remains in the design, the process is a substantial improvement over simple length matching.