SN75DP159: SI test Fail

Jeff

Do they have common mode choke on the output?

Thanks

David

Hi Daivd,

No common mode choke on the output side. thank!

Jeff

Jeff

Please add the appropriate common mode choke as it will help passing the intra-pair skew test.

Thanks

David

Hi David,

Caused add common mode choke need change layout, is possible to adjust EQ or slew to improve?

Thanks!

Jeff

Jeff

Part of the intra-pair skew comes from the board itself because the PCB manufacturing inconsistency. A common mode choke coil has the same configuration as a transformer, so when the timing of the rising and falling edges of the two lines is unbalanced, the common mode choke coil can ensure the currents are balanced by generating induced electromotive force on the opposite side. This behavior has the result of aligning the timing of the differential signals, thereby improving the intra-pair skew. 

You can try to change the slew rate and see if it helps, but having the choke on the output will help addressing the skew issue.

Thanks

David