HDMI/DVI Intra-pair and Inter-pair skew

Lakshmi Santosh

Other Parts Discussed in Thread: AM3894, DS16EV5110A, TFP410

Hello,

Need clarification on intra-pair and inter-pair skew for TMDS signals (HDMI or DVI) at source connector. Per HDMI spec, @ 225MHz, intra-pair skew is 66ps and inter-pair skew spec is 888ps at source connector. I also found that @165Mhz, intra-pair skew spec is < 90ps and inter-pair skew spec.

What is the max intra-pair and inter-pair skew allowed for TMDS differential traces from TI devices like AM3894, TFP410, DS16EV5110A etc ? The max frequency is 165MHz. Considering about 130-150ps propagation delay for every 1 inch and using the above number, intra-pair skew can be < 600mils and inter-pair skew can be < 8". Even if we consider the soure IC skew, ESD parasitics skew and connector skew, there is still a lot of margin. What is TI's recommendation ? In general I have seen 1" inter-pair skew spec and 5mils intra-pair skew spec which is much lower than what the spec mentions. Am I missing anything ? Please clarify.

Thanks,

Lakshmi

over 12 years ago

0 Elias Villegas M. over 12 years ago

TI__Guru* 76130 points

Hello,

I can tell about the TFP410 tha the intra-pair length mismatch is recommended to be less than 5mils, inter-pair length mismatch is less of a concern but the recommendation is to keep the traces <2" and keep the clock slightly longer than the data traces.

Regards.

0 Lakshmi Santosh over 12 years ago in reply to Elias Villegas M.

Intellectual 380 points

Thanks for that feedback. Is there any documentation that provides these specs and explains them ? The HDMI design guide does not provide the info you mentioned.

Thanks,

Lakshmi