Can HDMI cancel the series capacitor and pull up 499R design?
What are the functions of series capacitors and pull-up resistors?What will be the effect of the cancellation?
Any Suggestions you have will be helpful,thanks
0.1UF cap is for signal AC coupled, it is must have.
Pull-down resistors are must-to-have for HDMI connector use case. Reason is:
For each data/clock line, HDMI spec requires its single ended output swing voltage (Vswing) to be between 400mV and 600mV, with maximum high level voltage to be <= Avcc (3.3V) + 10mV
At HDMI sink side (e.g. LCD monitor), data/clock signals will be terminated to AVcc (3.3V) through 50ohm resistor (single end). Therefore:
If no pull-down resistors at source side, DC level at sink side will be 3.3V, then there will be no headroom for any positive voltage swing
With 499ohm pull-down resistors at source side, DC level at sink side will be: 3.3V*499/(499+50) = 2.999V, which can provide required headroom for both positive and negative voltage swing
Similarly for video serializer use case, please also double check the DC level inside serializer chip. If this DC level cannot provide enough headroom for Vswing, pull-down resistors will also be required.
Common mode chokes are for EMC purpose. If you don’t care EMI performance of HDMI connector due to its development purpose, then it’s fine to remove the common mode chokes.